The Ocean and Cryosphere in a Changing Climate This Summary for Policymakers was formally approved at the Second Joint Session of Working Groups I and II of the IPCC and accepted by the 51th Session of the IPCC, Principality of Monaco, 24th September 2019 Summary for Policymakers WG I WG II APPROVED SPM IPCC SR Ocean and Cryosphere Summary for Policymakers Drafting Authors: Nerilie Abram (Australia), Carolina Adler (Switzerland/Australia), Nathaniel L. Bindoff (Australia), Lijing Cheng (China), So-Min Cheong (Republic of Korea), William W. L. Cheung (Canada), Matthew Collins (UK), Chris Derksen (Canada), Alexey Ekaykin (Russian Federation), Thomas Frölicher (Switzerland), Matthias Garschagen (Germany), Jean-Pierre Gattuso (France), Bruce Glavovic (New Zealand), Stephan Gruber (Canada/Germany), Valeria Guinder (Argentina), Robert Hallberg (USA), Sherilee Harper (Canada), Nathalie Hilmi (Monaco/France), Jochen Hinkel (Germany), Yukiko Hirabayashi (Japan), Regine Hock (USA), Anne Hollowed (USA), Helene Jacot Des Combes (Fiji), James Kairo (Kenya), Alexandre K. Magnan (France), Valérie Masson-Delmotte (France), J.B. Robin Matthews (UK), Kathleen McInnes (Australia), Michael Meredith (UK), Katja Mintenbeck (Germany), Samuel Morin (France), Andrew Okem (South Africa/Nigeria), Michael Oppenheimer (USA), Ben Orlove (USA), Jan Petzold (Germany), Anna Pirani (Italy), Elvira Poloczanska (UK/Australia), Hans-Otto Pörtner (Germany), Anjal Prakash (Nepal/India), Golam Rasul (Nepal), Evelia Rivera-Arriaga (Mexico), Debra C. Roberts (South Africa), Edward A.G. Schuur (USA), Zita Sebesvari (Hungary/Germany), Martin Sommerkorn (Norway/Germany), Michael Sutherland (Trinidad and Tobago), Alessandro Tagliabue (UK), Roderik Van De Wal (Netherlands), Phil Williamson (UK), Rong Yu (China), Panmao Zhai (China) Draft Contributing Authors: Andrés Alegria (Honduras), Robert M. DeConto (USA), Andreas Fischlin (Switzerland), Shengping He (Norway/China), Miriam Jackson (Norway), Martin Künsting (Germany), Erwin Lambert (Netherlands), Pierre-Marie Lefeuvre (Norway/France), Alexander Milner (UK), Jess Melbourne-Thomas (Australia), Benoit Meyssignac (France), Maike Nicolai (Germany), Hamish Pritchard (UK), Heidi Steltzer (USA), Nora M. Weyer (Germany) DATE: 24 September 2019 This Summary for Policymakers should be cited as: IPCC, 2019: Summary for Policymakers. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.O. Pörtner, D.C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, M. Nicolai, A. Okem, J. Petzold, B. Rama, N. Weyer (eds.)]. In press. Subject to Copyedit SPM-1 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere Introduction This Special Report on the Ocean and Cryosphere1 in a Changing Climate (SROCC) was prepared following an IPCC Panel decision in 2016 to prepare three Special Reports during the Sixth Assessment Cycle2. By assessing new scientific literature3, the SROCC4 responds to government and observer organization proposals. The SROCC follows the other two Special Reports on Global Warming of 1.5°C (SR1.5) and on Climate Change and Land (SRCCL)5 and the Intergovernmental Science Policy Platform on Biodiversity and Ecosystem Services (IPBES) Global Assessment Report on Biodiversity and Ecosystem Services. This Summary for Policymakers (SPM) compiles key findings of the report and is structured in three parts: SPM.A: Observed changes and impacts, SPM.B: Projected changes and risks, and SPM.C: Implementing Responses to Ocean and Cryosphere Change. To assist navigation of the SPM, icons indicate where content can be found. Confidence in key findings is reported using IPCC calibrated language66 and the underlying scientific basis for each key finding is indicated by references to sections of the underlying report. Key of icons to indicate content The cryosphere is defined in this report (Annex I: Glossary) as the components of the Earth System at and below the land and ocean surface that are frozen, including snow cover, glaciers, ice sheets, ice shelves, icebergs, sea ice, lake ice, river ice, permafrost, and seasonally frozen ground. 1 The decision to prepare a Special Report on Climate Change and Oceans and the Cryosphere was made at the Forty-Third Session of the IPCC in Nairobi, Kenya, 11-13 April 2016. 2 3 Cut-off dates: 15 October 2018 for manuscript submission, 15 May 2019 for acceptance for publication. The SROCC is produced under the scientific leadership of Working Group I and Working Group II. In line with the approved outline, mitigation options (Working Group III) are not assessed with the exception of the mitigation potential of blue carbon (coastal ecosystems). 4 The full titles of these two Special Reports are: “Global Warming of 1.5°C. An IPCC special report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty”; “Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems”. 5 6 Each finding is grounded in an evaluation of underlying evidence and agreement. A level of confidence is expressed using five qualifiers: very low, low, medium, high and very high, and typeset in italics, e.g., medium confidence. The following terms have been used to indicate the assessed likelihood of an outcome or a result: virtually certain 99–100% probability, very likely 90–100%, likely 66–100%, about as likely as not 33–66%, unlikely 0–33%, very unlikely 0–10%, exceptionally unlikely 0–1%. Assessed likelihood is typeset in italics, e.g., very likely. This is consistent with AR5 and the other AR6 Special Reports. Additional terms (extremely likely 95–100%, more likely than not >50–100%, more unlikely than likely 0–<50%, extremely unlikely 0–5%) are used when appropriate. This Report also uses the term ‘likely range’ or ‘very likely range’ to indicate that the assessed likelihood of an outcome lies within the 17-83% or 5-95% probability range. For more details see {1.9.2, Figure 1.4} Subject to Copyedit SPM-2 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere Startup Box: The importance of the ocean and cryosphere for people All people on Earth depend directly or indirectly on the ocean and cryosphere. The global ocean covers 71% of the Earth surface and contains about 97% of the Earth’s water. The cryosphere refers to frozen components of the Earth system1. Around 10% of Earth’s land area is covered by glaciers or ice sheets. The ocean and cryosphere support unique habitats, and are interconnected with other components of the climate system through global exchange of water, energy and carbon. The projected responses of the ocean and cryosphere to past and current human-induced greenhouse gas emissions and ongoing global warming include climate feedbacks, changes over decades to millennia that cannot be avoided, thresholds of abrupt change, and irreversibility. {Box 1.1, 1.2} Human communities in close connection with coastal environments, small islands (including Small Island Developing States, SIDS), polar areas and high mountains7 are particularly exposed to ocean and cryosphere change, such as sea level rise, extreme sea level and shrinking cryosphere. Other communities further from the coast are also exposed to changes in the ocean, such as through extreme weather events. Today, around 4 million people live permanently in the Arctic region, of whom 10% are Indigenous. The low-lying coastal zone8 is currently home to around 680 million people (nearly 10% of the 2010 global population), projected to reach more than one billion by 2050. SIDS are home to 65 million people. Around 670 million people (nearly 10% of the 2010 global population), including Indigenous peoples, live in high mountain regions in all continents except Antarctica. In high mountain regions, population is projected to reach between 740 and 840 million by 2050 (about 8.4–8.7% of the projected global population). {1.1, 2.1, 3.1, Cross-Chapter Box 9, Figure 2.1} In addition to their role within the climate system, such as the uptake and redistribution of natural and anthropogenic carbon dioxide (CO2) and heat, as well as ecosystem support, services provided to people by the ocean and/or cryosphere include food and water supply, renewable energy, and benefits for health and well-being, cultural values, tourism, trade, and transport. The state of the ocean and cryosphere interacts with each aspect of sustainability reflected in the United Nations Sustainable Development Goals (SDGs). {1.1, 1.2, 1.5} 7 High mountain areas include all mountain regions where glaciers, snow or permafrost are prominent features of the landscape. For a list of high mountain regions covered in this report, see Chapter 2. Population in high mountain regions is calculated for areas less than 100 kilometres from glaciers or permafrost in high mountain areas assessed in this report {2.1}. Projections for 2050 give the range of population in these regions across all five of the Shared Socioeconomic Pathways {Cross-Chapter Box 1 in Chapter 1}. Population in the low elevation coastal zone is calculated for land areas connected to the coast, including small island states, that are less than 10 metres above sea level {Cross-Chapter Box 9}. Projections for 2050 give the range of population in these regions across all five of the Shared Socioeconomic Pathways {Cross-Chapter Box 1 in Chapter 1}. 8 Subject to Copyedit SPM-3 Total pages: 42 APPROVED SPM SPM.A IPCC SR Ocean and Cryosphere OBSERVED CHANGES AND IMPACTS Observed Physical Changes A1. Over the last decades, global warming has led to widespread shrinking of the cryosphere, with mass loss from ice sheets and glaciers (very high confidence), reductions in snow cover (high confidence) and Arctic sea ice extent and thickness (very high confidence), and increased permafrost temperature (very high confidence). {2.2, 3.2, 3.3, 3.4, Figures SPM.1, SPM.2} A1.1 Ice sheets and glaciers worldwide have lost mass (very high confidence). Between 2006 and 2015, the Greenland Ice Sheet9 lost ice mass at an average rate of 278 ± 11 Gt yr–1 (equivalent to 0.77 ± 0.03 mm yr–1 of global sea level rise), mostly due to surface melting (high confidence). In 2006–2015, the Antarctic Ice Sheet10 lost mass at an average rate of 155 ± 19 Gt yr–1 (0.43 ± 0.05 mm yr–1), mostly due to rapid thinning and retreat of major outlet glaciers draining the West Antarctic Ice Sheet (very high confidence). Glaciers worldwide outside Greenland and Antarctica lost mass at an average rate of 220 ± 30 Gt yr–1 (equivalent to 0.61 ± 0.08 mm yr–1 sea level rise) in 2006–2015. {3.3.1, 4.2.3, Appendix 2.A, Figure SPM.1} A1.2 Arctic June snow cover extent on land declined by 13.4 ± 5.4% per decade from 1967 to 2018, a total loss of approximately 2.5 million km2, predominantly due to surface air temperature increase (high confidence). In nearly all high mountain areas, the depth, extent and duration of snow cover have declined over recent decades, especially at lower elevation (high confidence). {2.2.2, 3.4.1, Figure SPM.1} A1.3 Permafrost temperatures have increased to record high levels (1980s-present) (very high confidence) including the recent increase by 0.29°C ± 0.12°C from 2007 to 2016 averaged across polar and highmountain regions globally. Arctic and boreal permafrost contain 1460–1600 Gt organic carbon, almost twice the carbon in the atmosphere (medium confidence). There is medium evidence with low agreement whether northern permafrost regions are currently releasing additional net methane and CO2 due to thaw. Permafrost thaw and glacier retreat have decreased the stability of high-mountain slopes (high confidence). {2.2.4, 2.3.2, 3.4.1, 3.4.3, Figure SPM.1} A1.4 Between 1979 and 2018, Arctic sea ice extent has very likely decreased for all months of the year. September sea ice reductions are very likely 12.8 ± 2.3% per decade. These sea ice changes in September are likely unprecedented for at least 1000 years. Arctic sea ice has thinned, concurrent with a transition to younger ice: between 9 Including peripheral glaciers 10 360 Gt ice corresponds to 1 mm of global mean sea level Subject to Copyedit SPM-4 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere 1979 and 2018, the areal proportion of multi-year ice at least five years old has declined by approximately 90% (very high confidence). Feedbacks from the loss of summer sea ice and spring snow cover on land have contributed to amplified warming in the Arctic (high confidence) where surface air temperature likely increased by more than double the global average over the last two decades. Changes in Arctic sea ice have the potential to influence mid-latitude weather (medium confidence), but there is low confidence in the detection of this influence for specific weather types. Antarctic sea ice extent overall has had no statistically significant trend (1979–2018) due to contrasting regional signals and large interannual variability (high confidence). {3.2.1, 6.3.1; Box 3.1; Box 3.2; A1.2, Figures SPM.1, SPM.2} Subject to Copyedit SPM-5 Total pages: 42 APPROVED SPM Subject to Copyedit IPCC SR Ocean and Cryosphere SPM-6 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere Figure SPM.1: Observed and modelled historical changes in the ocean and cryosphere since 195011, and projected future changes under low (RCP2.6) and high (RCP8.5) greenhouse gas emissions scenarios. {Box SPM.1}. Changes are shown for: (a) Global mean surface air temperature change with likely range {Box SPM.1, Cross-Chapter Box 1 in Chapter 1}. Ocean-related changes with very likely ranges for (b) Global mean sea surface temperature change {Box 5.1, 5.2.2}; (c) Change factor in surface ocean marine heatwave days {6.4.1}; (d) Global ocean heat content change (0–2000 m depth). An approximate steric sea level equivalent is shown with the right axis by multiplying the ocean heat content by the global-mean thermal expansion coefficient (ε ≈ 0.125 m per 1024 Joules)12 for observed warming since 1970 {Figure 5.1}; (h) Global mean surface pH (on the total scale). Assessed observational trends are compiled from open ocean time series sites longer than 15 years {Box 5.1, Figure 5.6, 5.2.2}; and (i) Global mean ocean oxygen change (100– 600 m depth). Assessed observational trends span 1970–2010 centered on 1996 {Figure 5.8, 5.2.2}. Sea-level changes with likely ranges for (m) Global mean sea level change. Hashed shading reflects low confidence in sea level projections beyond 2100 and bars at 2300 reflect expert elicitation on the range of possible sea level change {4.2.3, Figure 4.2}; and components from (e,f) Greenland and Antarctic ice sheet mass loss {3.3.1}; and (g) Glacier mass loss {Cross-Chapter Box 6 in Chapter 2, Table 4.1}. Further cryosphererelated changes with very likely ranges for (j) Arctic sea ice extent change for September13 {3.2.1, 3.2.2 Figure 3.3}; (k) Arctic snow cover change for June (land areas north of 60°N) {3.4.1, 3.4.2, Figure 3.10}; and (l) Change in near-surface (within 3–4 m) permafrost area in the Northern Hemisphere {3.4.1, 3.4.2, Figure 3.10}. Assessments of projected changes under the intermediate RCP4.5 and RCP6.0 scenarios are not available for all variables considered here, but where available can be found in the underlying report {For RCP4.5 see: 2.2.2, Cross-Chapter Box 6 in Chapter 2, 3.2.2, 3.4.2, 4.2.3, for RCP6.0 see Cross-Chapter Box 1 in Chapter 1}. Box SPM.1: Use of climate change scenarios in SROCC Assessments of projected future changes in this report are based largely on CMIP514 climate model projections using Representative Concentration Pathways (RCPs). RCPs are scenarios that include time series of emissions and concentrations of the full suite of greenhouse gases (GHGs) and aerosols and chemically active gases, as well as land use / land cover. RCPs provide only one set of many possible scenarios that would lead to different levels of global warming. {Annex I: Glossary} This report uses mainly RCP2.6 and RCP8.5 in its assessment, reflecting the available literature. RCP2.6 represents a low greenhouse gas emission, high mitigation future, that in CMIP5 simulations gives a two in three chance of limiting global warming to below 2°C by 2100 15. By contrast, RCP8.5 is a high greenhouse gas emission scenario in the absence of policies to combat climate change, leading to continued and sustained growth in atmospheric greenhouse gas 11 This does not imply that the changes started in 1950. Changes in some variables have occurred since the pre-industrial period. This scaling factor (global-mean ocean expansion as sea level rise in metres per unit heat) varies by about 10% between different models, and it will systematically increase by about 10% by 2100 under RCP8.5 forcing due to ocean warming increasing the average thermal expansion coefficient. {4.2.1, 4.2.2, 5.2.2} 12 13 Antarctic sea ice is not shown here due to low confidence in future projections. {3.2.2} 14 CMIP5 is Phase 5 of the Coupled Model Intercomparison Project (Annex I: Glossary). A pathway with lower emissions (RCP1.9), which would correspond to a lower level of projected warming than RCP2.6, was not part of CMIP5. 15 Subject to Copyedit SPM-7 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere concentrations. Compared to the total set of RCPs, RCP8.5 corresponds to the pathway with the highest greenhouse gas emissions. The underlying chapters also reference other scenarios, including RCP4.5 and RCP6.0 that have intermediate levels of greenhouse gas emissions and result in intermediate levels of warming. {Annex I: Glossary, Cross-Chapter Box 1 in Chapter 1} Table SPM.1 provides estimates of total warming since the pre-industrial period under four different RCPs for key assessment intervals used in SROCC. The warming from the 1850–1900 period until 1986–2005 has been assessed as 0.63°C (0.57 to 0.69°C likely range) using observations of near-surface air temperature over the ocean and over landy. Consistent with the approach in AR5, modelled future changes in global mean surface air temperature relative to 1986– 2005 are added to this observed warming. {Cross-Chapter Box 1 in Chapter 1} Table SPM.1: Projected global mean surface temperature change relative to 1850–1900 for two time periods under four RCPs16. Near-term: 2031–2050 End-of-century: 2081–2100 Scenario Mean (°C) likely range (°C) Mean (°C) likely range (°C) RCP2.6 1.6 1.1 to 2.0 1.6 0.9 to 2.4 RCP4.5 1.7 1.3 to 2.2 2.5 1.7 to 3.3 RCP6.0 1.6 1.2 to 2.0 2.9 2.0 to 3.8 RCP8.5 2.0 1.5 to 2.4 4.3 3.2 to 5.4 {Cross-Chapter Box 1 in Chapter 1} A2. It is virtually certain that the global ocean has warmed unabated since 1970 and has taken up more than 90% of the excess heat in the climate system (high confidence). Since 1993, the rate of ocean warming has more than doubled (likely). Marine heatwaves have very likely doubled in frequency since 1982 and are increasing in intensity (very high confidence). By absorbing more CO2, the ocean has undergone increasing surface acidification (virtually certain). A loss of oxygen has occurred from the surface to 1000 m (medium confidence). {1.4, 3.2, 5.2, 6.4, 6.7, Figures SPM.1, SPM.2} 16 In some instances this report assesses changes relative to 2006–2015. The warming from the 1850–1900 period until 2006–2015 has been assessed as 0.87°C (0.75 to 0.99°C likely range). {Cross-Chapter Box 1 in Chapter 1}. Subject to Copyedit SPM-8 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere A2.1. The ocean warming trend documented in the IPCC Fifth Assessment Report (AR5) has continued. Since 1993 the rate of ocean warming and thus heat uptake has more than doubled (likely)from 3.22 ± 1.61 ZJ yr–1 (0– 700 m depth) and 0.97 ± 0.64 ZJ yr–1 (700–2000 m) between 1969 and 1993, to 6.28 ± 0.48 ZJ yr–1 (0–700 m) and 3.86 ± 2.09 ZJ yr–1 (700–2000 m) between 1993 and 201717, and is attributed to anthropogenic forcing (very likely). {1.4.1, 5.2.2, Table 5.1, Figure SPM.1} A2.2 The Southern Ocean accounted for 35–43% of the total heat gain in the upper 2000 m global ocean between 1970 and 2017 (high confidence). Its share increased to 45–62% between 2005 and 2017 (high confidence). The deep ocean below 2000 m has warmed since 1992 (likely), especially in the Southern Ocean. {1.4, 3.2.1, 5.2.2, Table 5.1, Figure SPM.2} A2.3 Globally, marine heat related events have increased; marine heatwaves18, defined when the daily sea surface temperature exceeds the local 99th percentile over the period 1982 to 2016, have doubled in frequency and have become longer-lasting, more intense and more extensive (very likely). It is very likely that between 84–90% of marine heatwaves that occurred between 2006 and 2015 are attributable to the anthropogenic temperature increase. {Table 6.2, 6.4; Figures SPM.1, SPM.2} A2.4 Density stratification19 has increased in the upper 200 m of the ocean since 1970 (very likely). Observed surface ocean warming and high latitude addition of freshwater are making the surface ocean less dense relative to deeper parts of the ocean (high confidence) and inhibiting mixing between surface and deeper waters (high confidence). The mean stratification of the upper 200 m has increased by 2.3 ± 0.1% (very likely range) from the 1971–1990 average to the 1998–2017 average. {5.2.2} A2.5 The ocean has taken up between 20–30% (very likely) of total anthropogenic CO2 emissions since the 1980s causing further ocean acidification. Open ocean surface pH has declined by a very likely range of 0.017–0.027 pH units per decade since the late 1980s20, with the decline in surface ocean pH very likely to have already emerged from background natural variability for more than 95% of the ocean surface area. {3.2.1; 5.2.2; Box 5.1; Figures SPM.1, SPM.2} ZJ is Zettajoule and is equal to 1021 Joules. Warming the entire ocean by 1°C requires about 5500 ZJ; 144 ZJ would warm the top 100 m by about 1°C. 17 A marine heatwave is a period of extreme warm near-sea surface temperature that persists for days to months and can extend up to thousands of kilometres (Annex I: Glossary). 18 In this report density stratification is defined as the density contrast between shallower and deeper layers. Increased stratification reduces the vertical exchange of heat, salinity, oxygen, carbon, and nutrients. 19 20 Based on in-situ records longer than fifteen years. Subject to Copyedit SPM-9 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere A2.6 Datasets spanning 1970–2010 show that the open ocean has lost oxygen by a very likely range of 0.5–3.3% over the upper 1000 m, alongside a likely expansion of the volume of oxygen minimum zones by 3–8% (medium confidence). Oxygen loss is primarily due to increasing ocean stratification, changing ventilation and biogeochemistry (high confidence). {5.2.2; Figures SPM.1, SPM.2} A2.7 Observations, both in situ (2004–2017) and based on sea surface temperature reconstructions, indicate that the Atlantic Meridional Overturning Circulation (AMOC)21 has weakened relative to 1850–1900 (medium confidence). There is insufficient data to quantify the magnitude of the weakening, or to properly attribute it to anthropogenic forcing due to the limited length of the observational record. Although attribution is currently not possible, CMIP5 model simulations of the period 1850–2015, on average, exhibit a weakening AMOC when driven by anthropogenic forcing. {6.7}. A3. Global mean sea level (GMSL) is rising, with acceleration in recent decades due to increasing rates of ice loss from the Greenland and Antarctic ice sheets (very high confidence), as well as continued glacier mass loss and ocean thermal expansion. Increases in tropical cyclone winds and rainfall, and increases in extreme waves, combined with relative sea level rise, exacerbate extreme sea level events and coastal hazards (high confidence). {3.3; 4.2; 6.2; 6.3; 6.8; Figures SPM.1, SPM.2, SPM.4, SPM.5} A3.1 Total GMSL rise for 1902–2015 is 0.16 m (likely range 0.12–0.21 m). The rate of GMSL rise for 2006–2015 of 3.6 mm yr–1 (3.1–4.1 mm yr–1, very likely range), is unprecedented over the last century (high confidence), and about 2.5 times the rate for 1901–1990 of 1.4 mm yr–1 (0.8– 2.0 mm yr–1, very likely range). The sum of ice sheet and glacier contributions over the period 2006–2015 is the dominant source of sea level rise (1.8 mm yr–1, very likely range 1.7–1.9 mm yr–1), exceeding the effect of thermal expansion of ocean water (1.4 mm yr–1, very likely range 1.1– 1.7 mm yr–1) 22 (very high confidence). The dominant cause of global mean sea level rise since 1970 is anthropogenic forcing (high confidence). {4.2.1, 4.2.2, Figure SPM.1} A3.2 Sea-level rise has accelerated (extremely likely) due to the combined increased ice loss from the Greenland and Antarctic ice sheets (very high confidence). Mass loss from the Antarctic ice sheet over the period 2007– 2016 tripled relative to 1997–2006. For Greenland, mass loss doubled over the same period (likely, medium confidence). {3.3.1; Figures SPM.1, SPM.2; SPM A1.1} 21 The Atlantic Meridional Overturning Circulation (AMOC) is the main current system in the South and North Atlantic Oceans (Annex I: Glossary). The total rate of sea-level rise is greater than the sum of cryosphere and ocean contributions due to uncertainties in the estimate of landwater storage. 22 Subject to Copyedit SPM-10 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere A3.3 Acceleration of ice flow and retreat in Antarctica, which has the potential to lead to sea-level rise of several metres within a few centuries, is observed in the Amundsen Sea Embayment of West Antarctica and in Wilkes Land, East Antarctica (very high confidence). These changes may be the onset of an irreversible23 ice sheet instability. Uncertainty related to the onset of ice sheet instability arises from limited observations, inadequate model representation of ice sheet processes, and limited understanding of the complex interactions between the atmosphere, ocean and the ice sheet. {3.3.1, Cross-Chapter Box 8 in Chapter 3, 4.2.3} A3.4 Sea-level rise is not globally uniform and varies regionally. Regional differences, within ±30% of the global mean sea-level rise, result from land ice loss and variations in ocean warming and circulation. Differences from the global mean can be greater in areas of rapid vertical land movement including from local human activities (e.g. extraction of groundwater). (high confidence) {4.2.2, 5.2.2, 6.2.2, 6.3.1, 6.8.2, Figure SPM.2} A3.5 Extreme wave heights, which contribute to extreme sea level events, coastal erosion and flooding, have increased in the Southern and North Atlantic Oceans by around 1.0 cm yr–1 and 0.8 cm yr–1 over the period 1985– 2018 (medium confidence). Sea ice loss in the Arctic has also increased wave heights over the period 1992–2014 (medium confidence). {4.2.2, 6.2, 6.3, 6.8, Box 6.1} A3.6 Anthropogenic climate change has increased observed precipitation (medium confidence), winds (low confidence), and extreme sea level events (high confidence) associated with some tropical cyclones, which has increased intensity of multiple extreme events and associated cascading impacts (high confidence). Anthropogenic climate change may have contributed to a poleward migration of maximum tropical cyclone intensity in the western North Pacific in recent decades related to anthropogenically-forced tropical expansion (low confidence). There is emerging evidence for an increase in annual global proportion of Category 4 or 5 tropical cyclones in recent decades (low confidence). {6.2, Table 6.2, 6.3, 6.8, Box 6.1} Observed Impacts on Ecosystems A4. Cryospheric and associated hydrological changes have impacted terrestrial and freshwater species and ecosystems in high mountain and polar regions through the appearance of land previously covered by ice, changes in snow cover, and thawing permafrost. These changes have contributed to changing the seasonal activities, abundance and distribution of ecologically, culturally, and economically important plant and animal species, ecological disturbances, and ecosystem functioning. (high confidence) {2.3.2, 2.3.3, 3.4.1, 3.4.3, Box 3.4, Figure SPM.2} 23 The recovery time scale is hundreds to thousands of years (Annex I: Glossary). Subject to Copyedit SPM-11 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere A4.1 Over the last century some species of plants and animals have increased in abundance, shifted their range, and established in new areas as glaciers receded and the snow-free season lengthened (high confidence). Together with warming, these changes have increased locally the number of species in high mountains, as lower-elevation species migrate upslope (very high confidence). Some cold-adapted or snow-dependent species have declined in abundance, increasing their risk of extinction, notably on mountain summits (high confidence). In polar and mountain regions, many species have altered seasonal activities especially in late winter and spring (high confidence). {2.3.3, Box 3.4} A4.2 Increased wildfire and abrupt permafrost thaw, as well as changes in Arctic and mountain hydrology have altered frequency and intensity of ecosystem disturbances (high confidence). This has included positive and negative impacts on vegetation and wildlife such as reindeer and salmon (high confidence). {2.3.3, 3.4.1, 3.4.3} A4.3 Across tundra, satellite observations show an overall greening, often indicative of increased plant productivity (high confidence). Some browning areas in tundra and boreal forest are indicative that productivity has decreased (high confidence). These changes have negatively affected provisioning, regulating and cultural ecosystem services, with also some transient positive impacts for provisioning services, in both high mountains (medium confidence) and polar regions (high confidence). {2.3.1, 2.3.3, 3.4.1, 3.4.3, Annex I: Glossary} A5. Since about 1950 many marine species across various groups have undergone shifts in geographical range and seasonal activities in response to ocean warming, sea ice change and biogeochemical changes, such as oxygen loss, to their habitats (high confidence). This has resulted in shifts in species composition, abundance and biomass production of ecosystems, from the equator to the poles. Altered interactions between species have caused cascading impacts on ecosystem structure and functioning (medium confidence). In some marine ecosystems species are impacted by both the effects of fishing and climate changes (medium confidence). {3.2.3, 3.2.4, Box 3.4, 5.2.3, 5.3, 5.4.1, Figure SPM.2} A5.1 Rates of poleward shifts in distributions across different marine species since the 1950s are 52 ± 33 km per decade and 29 ± 16 km per decade (very likely ranges) for organisms in the epipelagic (upper 200 m from sea surface) and seafloor ecosystems, respectively. The rate and direction of observed shifts in distributions are shaped by local temperature, oxygen, and ocean currents across depth, latitudinal and longitudinal gradients (high confidence). Warming-induced species range expansions have led to altered ecosystem structure and functioning such as in the North Atlantic, Northeast Pacific and Arctic (medium confidence). {5.2.3, 5.3.2, 5.3.6, Box 3.4, Figure SPM.2} A5.2 In recent decades, Arctic net primary production has increased in ice-free waters (high confidence) and spring phytoplankton blooms are occurring earlier in the year in response to sea ice change and nutrient availability Subject to Copyedit SPM-12 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere with spatially variable positive and negative consequences for marine ecosystems (medium confidence). In the Antarctic, such changes are spatially heterogeneous and have been associated with rapid local environmental change, including retreating glaciers and sea ice change (medium confidence). Changes in the seasonal activities, production and distribution of some Arctic zooplankton and a southward shift in the distribution of the Antarctic krill population in the South Atlantic are associated with climate-linked environmental changes (medium confidence). In polar regions, ice associated marine mammals and seabirds have experienced habitat contraction linked to sea ice changes (high confidence) and impacts on foraging success due to climate impacts on prey distributions (medium confidence). Cascading effects of multiple climaterelated drivers on polar zooplankton have affected food web structure and function, biodiversity as well as fisheries (high confidence). {3.2.3, 3.2.4, Box 3.4, 5.2.3, Figure SPM.2} A5.3 Eastern Boundary Upwelling Systems (EBUS) are amongst the most productive ocean ecosystems. Increasing ocean acidification and oxygen loss are negatively impacting two of the four major upwelling systems: the California Current and Humboldt Current (high confidence). Ocean acidification and decrease in oxygen level in the California Current upwelling system have altered ecosystem structure, with direct negative impacts on biomass production and species composition (medium confidence). {Box 5.3, Figure SPM.2} A5.4 Ocean warming in the 20th century and beyond has contributed to an overall decrease in maximum catch potential (medium confidence), compounding the impacts from overfishing for some fish stocks (high confidence). In many regions, declines in the abundance of fish and shellfish stocks due to direct and indirect effects of global warming and biogeochemical changes have already contributed to reduced fisheries catches (high confidence). In some areas, changing ocean conditions have contributed to the expansion of suitable habitat and/or increases in the abundance of some species (high confidence). These changes have been accompanied by changes in species composition of fisheries catches since the 1970s in many ecosystems (medium confidence). {3.2.3, 5.4.1, Figure SPM.2} A6. Coastal ecosystems are affected by ocean warming, including intensified marine heatwaves, acidification, loss of oxygen, salinity intrusion and sea level rise, in combination with adverse effects from human activities on ocean and land (high confidence). Impacts are already observed on habitat area and biodiversity, as well as ecosystem functioning and services (high confidence). {4.3.2, 4.3.3, 5.3, 5.4.1, 6.4.2, Figure SPM.2} A6.1 Vegetated coastal ecosystems protect the coastline from storms and erosion and help buffer the impacts of sea level rise. Nearly 50% of coastal wetlands have been lost over the last 100 years, as a result of the combined effects of localised human pressures, sea level rise, warming and extreme climate events (high confidence). Vegetated coastal ecosystems are important carbon stores; their loss is responsible for the current release of 0.04–1.46 GtC yr–1 (medium confidence). In response to warming, distribution ranges of seagrass meadows and kelp forests are expanding at high latitudes and contracting at low latitudes since the late 1970s (high confidence), and in some areas Subject to Copyedit SPM-13 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere episodic losses occur following heatwaves (medium confidence). Large-scale mangrove mortality that is related to warming since the 1960s has been partially offset by their encroachment into subtropical saltmarshes as a result of increase in temperature, causing the loss of open areas with herbaceous plants that provide food and habitat for dependent fauna (high confidence). {4.3.3, 5.3.2, 5.3.6, 5.4.1, 5.5.1, Figure SPM.2}. A6.2 Increased sea water intrusion in estuaries due to sea level rise has driven upstream redistribution of marine species (medium confidence) and caused a reduction of suitable habitats for estuarine communities (medium confidence). Increased nutrient and organic matter loads in estuaries since the 1970s from intensive human development and riverine loads have exacerbated the stimulating effects of ocean warming on bacterial respiration, leading to expansion of low oxygen areas (high confidence). {5.3.1}. A6.3 The impacts of sea level rise on coastal ecosystems include habitat contraction, geographical shift of associated species, and loss of biodiversity and ecosystem functionality. Impacts are exacerbated by direct human disturbances, and where anthropogenic barriers prevent landward shift of marshes and mangroves (termed coastal squeeze) (high confidence). Depending on local geomorphology and sediment supply, marshes and mangroves can grow vertically at rates equal to or greater than current mean sea level rise (high confidence). {4.3.2, 4.3.3, 5.3.2, 5.3.7, 5.4.1} A6.4 Warm-water coral reefs and rocky shores dominated by immobile, calcifying (e.g., shell and skeleton producing) organisms such as corals, barnacles and mussels, are currently impacted by extreme temperatures and ocean acidification (high confidence). Marine heatwaves have already resulted in large-scale coral bleaching events at increasing frequency (very high confidence) causing worldwide reef degradation since 1997, and recovery is slow (more than 15 years) if it occurs (high confidence). Prolonged periods of high environmental temperature and dehydration of the organisms pose high risk to rocky shore ecosystems (high confidence). {SR1.5; 5.3.4, 5.3.5, 6.4.2.1, Figure SPM.2} Subject to Copyedit SPM-14 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere Figure SPM.2: Synthesis of observed regional hazards and impacts in ocean 24 (top) and high mountain and polar land regions (bottom) assessed in SROCC. For each region, physical changes, impacts on key ecosystems, and impacts on human systems and ecosystem function and services are shown. For physical changes, yellow/green refers to an increase/decrease, respectively, in amount or frequency of the measured variable. For impacts on ecosystems, human systems and ecosystems services blue or red depicts whether an observed impact is positive (beneficial) or negative (adverse), respectively, to the given system or service. Cells assigned ‘increase and decrease’ indicate that within that region, both increase and decrease of physical changes are found, but are not necessarily equal; the same holds for cells showing ‘positive and negative’ attributable impacts. For ocean regions, the confidence level refers to the confidence in attributing observed changes to changes in greenhouse gas forcing for physical changes and to climate change for ecosystem, human systems, and ecosystem services. For high-mountain and polar land regions, the level of confidence in attributing physical changes and impacts at least partly to a change in the cryosphere is shown. No assessment means: not applicable, not assessed at regional scale, or the evidence is insufficient for assessment. The physical changes in the ocean are defined as: Temperature change in 0–700 m layer of the ocean except for Southern Ocean (0–2000 m) and Arctic Ocean (upper mixed layer and major inflowing 24 Marginal seas are not assessed individually as ocean regions in this report. Subject to Copyedit SPM-15 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere branches); Oxygen in the 0–1200 m layer or oxygen minimum layer; Ocean pH as surface pH (decreasing pH corresponds to increasing ocean acidification). Ecosystems in the ocean: Coral refers to warm-water coral reefs and cold-water corals. The ‘upper water column’ category refers to epipelagic zone for all ocean regions except Polar Regions, where the impacts on some pelagic organisms in open water deeper than the upper 200 m were included. Coastal wetland includes salt marshes, mangroves and seagrasses. Kelp forests are habitats of a specific group of macroalgae. Rocky shores are coastal habitats dominated by immobile calcified organisms such as mussels and barnacles. Deep sea is seafloor ecosystems that are 3000–6000 m deep. Sea-ice associated includes ecosystems in, on and below sea ice. Habitat services refer to supporting structures and services (e.g., habitat, biodiversity, primary production). Coastal Carbon Sequestration refers to the uptake and storage of carbon by coastal blue carbon ecosystems. Ecosystems on Land: Tundra refers to tundra and alpine meadows, and includes terrestrial Antarctic ecosystems. Migration refers to an increase or decrease in net migration, not to beneficial/adverse value. Impacts on tourism refer to the operating conditions for the tourism sector. Cultural services include cultural identity, sense of home, and spiritual, intrinsic and aesthetic values, as well as contributions from glacier archaeology. The underlying information is given for land regions in tables SM2.6, SM2.7, SM2.8, SM3.8, SM3.9, and SM3.10, and for ocean regions in tables SM5.10, SM5.11, SM3.8, SM3.9, and SM3.10. {2.3.1, 2.3.2, 2.3.3, 2.3.4, 2.3.5, 2.3.6, 2.3.7, Figure 2.1, 3.2.1; 3.2.3; 3.2.4; 3.3.3; 3.4.1; 3.4.3; 3.5.2; Box 3.4, 4.2.2, 5.2.2, 5.2.3, 5.3.3, 5.4, 5.6, Figure 5.24, Box 5.3} Observed Impacts on People and Ecosystem Services A7. Since the mid-20th century, the shrinking cryosphere in the Arctic and high-mountain areas has led to predominantly negative impacts on food security, water resources, water quality, livelihoods, health and well-being, infrastructure, transportation, tourism and recreation, as well as culture of human societies, particularly for Indigenous peoples (high confidence). Costs and benefits have been unequally distributed across populations and regions. Adaptation efforts have benefited from the inclusion of Indigenous knowledge and local knowledge (high confidence). {1.1, 1.5, 1.6.2, 2.3, 2.4, 3.4, 3.5, Figure SPM.2} A7.1 Food and water security have been negatively impacted by changes in snow cover, lake and river ice, and permafrost in many Arctic regions (high confidence). These changes have disrupted access to, and food availability within, herding, hunting, fishing, and gathering areas, harming the livelihoods and cultural identity of Arctic residents including Indigenous populations (high confidence). Glacier retreat and snow cover changes have contributed to localized declines in agricultural yields in some high mountain regions, including Hindu Kush Himalaya and the tropical Andes (medium confidence). {2.3.1., 2.3.7, Box 2.4, 3.4.1, 3.4.2, 3.4.3, 3.5.2, Figure SPM.2} A7.2 In the Arctic, negative impacts of cryosphere change on human health have included increased risk of food- and waterborne diseases, malnutrition, injury, and mental health challenges especially among Indigenous peoples (high confidence). In some high-mountain areas, water quality has been affected by contaminants, particularly mercury, released from melting glaciers and thawing permafrost (medium confidence). Health-related adaptation efforts Subject to Copyedit SPM-16 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere in the Arctic range from local to international in scale, and successes have been underpinned by Indigenous knowledge (high confidence). {1.8, Cross-Chapter Box 4 in Chapter 1, 2.3.1, 3.4.3} A7.3 Arctic residents, especially Indigenous peoples, have adjusted the timing of activities to respond to changes in seasonality and safety of land, ice, and snow travel conditions. Municipalities and industry are beginning to address infrastructure failures associated with flooding and thawing permafrost and some coastal communities have planned for relocation (high confidence). Limited funding, skills, capacity, and institutional support to engage meaningfully in planning processes have challenged adaptation (high confidence). {3.5.2, 3.5.4, Cross-Chapter Box 9} A7.4 Summertime Arctic ship-based transportation (including tourism) increased over the past two decades concurrent with sea ice reductions (high confidence). This has implications for global trade and economies linked to traditional shipping corridors, and poses risks to Arctic marine ecosystems and coastal communities (high confidence), such as from invasive species and local pollution. {3.2.1, 3.2.4, 3.5.4, 5.4.2, Figure SPM.2} A7.5 In past decades, exposure of people and infrastructure to natural hazards has increased due to growing population, tourism and socioeconomic development (high confidence). Some disasters have been linked to changes in the cryosphere, for example in the Andes, high mountain Asia, Caucasus and European Alps (medium confidence). {2.3.2, Fig SPM.2} A7.6 Changes in snow and glaciers have changed the amount and seasonality of runoff and water resources in snow dominated and glacier-fed river basins (very high confidence). Hydropower facilities have experienced changes in seasonality and both increases and decreases in water input from high mountain areas, for example, in central Europe, Iceland, Western USA/Canada, and tropical Andes (medium confidence). However, there is only limited evidence of resulting impacts on operations and energy production. {B1.4, 2.3.1} A7.7 High mountain aesthetic and cultural aspects have been negatively impacted by glacier and snow cover decline (e.g. in the Himalaya, East Africa, the tropical Andes) (medium confidence). Tourism and recreation, including ski and glacier tourism, hiking, and mountaineering, have also been negatively impacted in many mountain regions (medium confidence). In some places, artificial snowmaking has reduced negative impacts on ski tourism (medium confidence). {2.3.5, 2.3.6, Figure SPM.2} A8. Changes in the ocean have impacted marine ecosystems and ecosystem services with regionally diverse outcomes, challenging their governance (high confidence). Both positive and negative impacts result for food security through fisheries (medium confidence), local cultures and livelihoods (medium confidence), and tourism and recreation (medium confidence). The impacts on ecosystem services have negative consequences for health and well-being (medium Subject to Copyedit SPM-17 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere confidence), and for Indigenous peoples and local communities dependent on fisheries (high confidence). {1.1, 1.5, 3.2.1, 5.4.1, 5.4.2, Figure SPM.2} A8.1 Warming-induced changes in the spatial distribution and abundance of some fish and shellfish stocks have had positive and negative impacts on catches, economic benefits, livelihoods, and local culture (high confidence). There are negative consequences for Indigenous peoples and local communities that are dependent on fisheries (high confidence). Shifts in species distributions and abundance has challenged international and national ocean and fisheries governance, including in the Arctic, North Atlantic and Pacific, in terms of regulating fishing to secure ecosystem integrity and sharing of resources between fishing entities (high confidence). {3.2.4, 3.5.3, 5.4.2, 5.5.2, Figure SPM.2} A8.2 Harmful algal blooms display range expansion and increased frequency in coastal areas since the 1980s in response to both climatic and non-climatic drivers such as increased riverine nutrients run-off (high confidence). The observed trends in harmful algal blooms are attributed partly to the effects of ocean warming, marine heatwaves, oxygen loss, eutrophication and pollution (high confidence). Harmful algal blooms have had negative impacts on food security, tourism, local economy, and human health (high confidence). The human communities who are more vulnerable to these biological hazards are those in areas without sustained monitoring programs and dedicated early warning systems for harmful algal blooms (medium confidence). {Box 5.4, 5.4.2, 6.4.2}. A9. Coastal communities are exposed to multiple climate-related hazards, including tropical cyclones, extreme sea levels and flooding, marine heatwaves, sea ice loss, and permafrost thaw (high confidence). A diversity of responses has been implemented worldwide, mostly after extreme events, but also some in anticipation of future sea level rise, e.g., in the case of large infrastructure. {3.2.4, 3.4.3, 4.3.2, 4.3.3, 4.3.4, 4.4.2, 5.4.2, 6.2, 6.4.2, 6.8, Box 6.1, Cross Chapter Box 9, Figure SPM.5} A9.1 Attribution of current coastal impacts on people to sea level rise remains difficult in most locations since impacts were exacerbated by human-induced non-climatic drivers, such as land subsidence (e.g., groundwater extraction), pollution, habitat degradation, reef and sand mining (high confidence). {4.3.2., 4.3.3} A9.2 Coastal protection through hard measures, such as dikes, seawalls, and surge barriers, is widespread in many coastal cities and deltas. Ecosystem-based and hybrid approaches combining ecosystems and built infrastructure are becoming more popular worldwide. Coastal advance, which refers to the creation of new land by building seawards (e.g., land reclamation), has a long history in most areas where there are dense coastal populations and a shortage of land. Coastal retreat, which refers to the removal of human occupation of coastal areas, is also observed, Subject to Copyedit SPM-18 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere but is generally restricted to small human communities or occurs to create coastal wetland habitat. The effectiveness of the responses to sea level rise are assessed in Figure SPM.5. {3.5.3, 4.3.3, 4.4.2, 6.3.3, 6.9.1, Cross-Chapter Box 9} SPM.B PROJECTED CHANGES AND RISKS Projected Physical Changes25 B1. Global-scale glacier mass loss, permafrost thaw, and decline in snow cover and Arctic sea ice extent are projected to continue in the near-term (2031–2050) due to surface air temperature increases (high confidence), with unavoidable consequences for river runoff and local hazards (high confidence). The Greenland and Antarctic Ice Sheets are projected to lose mass at an increasing rate throughout the 21st century and beyond (high confidence). The rates and magnitudes of these cryospheric changes are projected to increase further in the second half of the 21st century in a high greenhouse gas emissions scenario (high confidence). Strong reductions in greenhouse gas emissions in the coming decades are projected to reduce further changes after 2050 (high confidence). {2.2, 2.3, Cross-Chapter Box 6 in Chapter 2, 3.3, 3.4, Figure SPM.1, SPM Box SPM.1} B1.1 Projected glacier mass reductions between 2015 and 2100 (excluding the ice sheets) range from 18 ± 7% (likely range) for RCP2.6 to 36 ± 11% (likely range) for RCP8.5, corresponding to a sea-level contribution of 94 ± 25 mm (likely range) sea-level equivalent for RCP2.6, and 200 ± 44 mm (likely range) for RCP8.5 (medium confidence). Regions with mostly smaller glaciers (e.g., Central Europe, Caucasus, North Asia, Scandinavia, tropical Andes, Mexico, eastern Africa and Indonesia), are projected to lose more than 80% of their current ice mass by 2100 under RCP8.5 (medium confidence), and many glaciers are projected to disappear regardless of future emissions (very high confidence). {Cross-Chapter Box 6 in Chapter 2, Figure SPM.1} B1.2 In 2100, the Greenland Ice Sheet’s projected contribution to GMSL rise is 0.07 m (0.04–0.12 m, likely range) under RCP2.6, and 0.15 m (0.08–0.27 m, likely range) under RCP8.5. In 2100, the Antarctic Ice Sheet is projected to contribute 0.04 m (0.01–0.11 m, likely range) under RCP2.6, and 0.12 m (0.03–0.28 m, likely range) under RCP8.5. The Greenland Ice Sheet is currently contributing more to sea-level rise than the Antarctic Ice Sheet (high confidence), but Antarctica could become a larger contributor by the end of the 21st century as a consequence of rapid retreat (low confidence). Beyond 2100, increasing divergence between Greenland and Antarctica’s relative contributions to GMSL rise under RCP8.5 has important consequences for the pace of relative sea-level rise in the Northern Hemisphere. {3.3.1, 4.2.3, 4.2.5, 4.3.3, Cross-Chapter Box 8, Figure SPM.1} This report primarily uses RCP2.6 and RCP8.5 for the following reasons: These scenarios largely represent the assessed range for the topics covered in this report; they largely represent what is covered in the assessed literature, based on CMIP5; and they allow a consistent narrative about projected changes. RCP4.5 and RCP6.0 are not available for all topics addressed in the report. {Box SPM.1} 25 Subject to Copyedit SPM-19 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere B1.3 Arctic autumn and spring snow cover are projected to decrease by 5–10%, relative to 1986–2005, in the near-term (2031–2050), followed by no further losses under RCP2.6, but an additional 15–25% loss by the end of century under RCP8.5 (high confidence). In high mountain areas, projected decreases in low elevation mean winter snow depth, compared to 1986–2005, are likely 10–40% by 2031–2050, regardless of emissions scenario (high confidence). For 2081–2100, this projected decrease is likely 10–40 % for RCP2.6 and 50–90% for RCP8.5. {2.2.2, 3.3.2, 3.4.2, Figure SPM.1} B1.4 Widespread permafrost thaw is projected for this century (very high confidence) and beyond. By 2100, projected near-surface (within 3–4 m) permafrost area shows a decrease of 24 ± 16% (likely range) for RCP2.6 and 69 ± 20% (likely range) for RCP8.5. The RCP8.5 scenario leads to the cumulative release of tens to hundreds of billions of tons (GtC) of permafrost carbon as CO226 and methane to the atmosphere by 2100 with the potential to exacerbate climate change (medium confidence). Lower emissions scenarios dampen the response of carbon emissions from the permafrost region (high confidence). Methane contributes a small fraction of the total additional carbon release but is significant because of its higher warming potential. Increased plant growth is projected to replenish soil carbon in part, but will not match carbon releases over the long term (medium confidence). {2.2.4, 3.4.2, 3.4.3, Figure SPM.1, Cross-Chapter Box 5 in Chapter 1} B1.5 In many high mountain areas, glacier retreat and permafrost thaw are projected to further decrease the stability of slopes, and the number and area of glacier lakes will continue to increase (high confidence). Floods due to glacier lake outburst or rain-on-snow, landslides and snow avalanches, are projected to occur also in new locations or different seasons (high confidence). {2.3.2} B1.6 River runoff in snow-dominated or glacier-fed high mountain basins is projected to change regardless of emissions scenario (very high confidence), with increases in average winter runoff (high confidence) and earlier spring peaks (very high confidence). In all emissions scenarios, average annual and summer runoff from glaciers are projected to peak at or before the end of the 21st century (high confidence), e.g., around mid-century in High Mountain Asia, followed by a decline in glacier runoff. In regions with little glacier cover (e.g., tropical Andes, European Alps) most glaciers have already passed this peak (high confidence). Projected declines in glacier runoff by 2100 (RCP8.5) can reduce basin runoff by 10% or more in at least one month of the melt season in several large river basins, especially in High Mountain Asia during the dry season (low confidence). {2.3.1} For context, total annual anthropogenic CO2 emissions were 10.8 ± 0.8 GtC yr–1 (39.6 ± 2.9 GtCO2 yr–1) on average over the period 2008–2017. Total annual anthropogenic methane emissions were 0.35 ± 0.01 GtCH4 yr–1, on average over the period 2003–2012. {5.5.1} 26 Subject to Copyedit SPM-20 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere B1.7 Arctic sea ice loss is projected to continue through mid-century, with differences thereafter depending on the magnitude of global warming: for stabilised global warming of 1.5°C the annual probability of a sea ice free September by the end of century is approximately 1%, which rises to 10–35% for stabilised global warming of 2°C (high confidence). There is low confidence in projections for Antarctic sea ice. {3.2.2, Figure SPM.1} B2. Over the 21st century, the ocean is projected to transition to unprecedented conditions with increased temperatures (virtually certain), greater upper ocean stratification (very likely), further acidification (virtually certain), oxygen decline (medium confidence), and altered net primary production (low confidence). Marine heatwaves (very high confidence) and extreme El Niño and La Niña events (medium confidence) are projected to become more frequent. The Atlantic Meridional Overturning Circulation (AMOC) is projected to weaken (very likely). The rates and magnitudes of these changes will be smaller under scenarios with low greenhouse gas emissions (very likely). {3.2; 5.2; 6.4; 6.5; 6.7; Box 5.1; Figures SPM.1, SPM.3} B2.1 The ocean will continue to warm throughout the 21st century (virtually certain). By 2100, the top 2000 m of the ocean are projected to take up 5–7 times more heat under RCP8.5 (or 2–4 times more under RCP2.6) than the observed accumulated ocean heat uptake since 1970 (very likely). The annual mean density stratification14 of the top 200 m, averaged between 60°S and 60°N, is projected to increase by 12–30% for RCP8.5 and 1–9% for RCP2.6, for 2081–2100 relative to 1986–2005 (very likely), inhibiting vertical nutrient, carbon and oxygen fluxes. {5.2.2, Figure SPM.1} B2.2 By 2081–2100 under RCP8.5, ocean oxygen content (medium confidence), upper ocean nitrate content (medium confidence), net primary production (low confidence) and carbon export (medium confidence) are projected to decline globally by very likely ranges of 3–4%, 9–14%, 4–11% and 9-16% respectively, relative to 2006– 2015. Under RCP2.6, globally projected changes by 2081–2100 are smaller compared to RCP8.5 for oxygen loss (very likely), nutrient availability (about as likely as not) and net primary production (high confidence). {5.2.2; Box 5.1; Figures SPM.1, SPM.3} B2.3 Continued carbon uptake by the ocean by 2100 is virtually certain to exacerbate ocean acidification. Open ocean surface pH is projected to decrease by around 0.3 pH units by 2081–2100, relative to 2006– 2015, under RCP8.5 (virtually certain). For RCP8.5, there are elevated risks for keystone aragonite shell-forming species due to crossing an aragonite stability threshold year-round in the Polar and sub-Polar Oceans by 2081–2100 (very likely). For RCP2.6, these conditions will be avoided this century (very likely), but some eastern boundary upwelling systems are projected to remain vulnerable (high confidence). {3.2.3, 5.2.2, Box 5.1, Box 5.3, Figure SPM.1} Subject to Copyedit SPM-21 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere B2.4 Climate conditions, unprecedented since the preindustrial period, are developing in the ocean, elevating risks for open ocean ecosystems. Surface acidification and warming have already emerged in the historical period (very likely). Oxygen loss between 100 and 600 m depth is projected to emerge over 59–80% of the ocean area by 2031– 2050 under RCP8.5 (very likely). The projected time of emergence for five primary drivers of marine ecosystem change (surface warming and acidification, oxygen loss, nitrate content and net primary production change) are all prior to 2100 for over 60% of the ocean area under RCP8.5 and over 30% under RCP2.6 (very likely). {Annex I: Glossary, Box 5.1, Box 5.1 Figure 1} B2.5 Marine heatwaves are projected to further increase in frequency, duration, spatial extent and intensity (maximum temperature) (very high confidence). Climate models project increases in the frequency of marine heatwaves by 2081–2100, relative to 1850–1900, by approximately 50 times under RCP8.5 and 20 times under RCP2.6 (medium confidence). The largest increases in frequency are projected for the Arctic and the tropical oceans (medium confidence). The intensity of marine heatwaves is projected to increase about 10-fold under RCP8.5 by 2081–2100, relative to 1850–1900 (medium confidence).{6.4, Figure SPM.1} B2.6 Extreme El Niño and La Niña events are projected to likely increase in frequency in the 21st century and to likely intensify existing hazards, with drier or wetter responses in several regions across the globe. Extreme El Niño events are projected to occur about as twice as often under both RCP2.6 and RCP8.5 in the 21st century when compared to the 20th century (medium confidence). Projections indicate that extreme Indian Ocean Dipole events also increase in frequency (low confidence). {6.5; Figures 6.5, 6.6} B2.7 The AMOC is projected to weaken in the 21st century under all RCPs (very likely), although a collapse is very unlikely (medium confidence). Based on CMIP5 projections, by 2300, an AMOC collapse is as likely as not for high emissions scenarios and very unlikely for lower ones (medium confidence). Any substantial weakening of the AMOC is projected to cause a decrease in marine productivity in the North Atlantic (medium confidence), more storms in Northern Europe (medium confidence), less Sahelian summer rainfall (high confidence) and South Asian summer rainfall (medium confidence), a reduced number of tropical cyclones in the Atlantic (medium confidence), and an increase in regional sea level along the northeast coast of North America (medium confidence). Such changes would be in addition to the global warming signal. {6.7; Figures 6.8–6.10} B3. Sea level continues to rise at an increasing rate. Extreme sea level events that are historically rare (once per century in the recent past) are projected to occur frequently (at least once per year) at many locations by 2050 in all RCP scenarios, especially in tropical regions (high confidence). The increasing frequency of high water levels can have severe impacts in many locations depending on exposure (high confidence). Sea level rise is projected to continue beyond 2100 in all RCP scenarios. For a high emissions scenario (RCP8.5), projections of global sea level rise by 2100 are greater than in AR5 Subject to Copyedit SPM-22 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere due to a larger contribution from the Antarctic Ice Sheet (medium confidence). In coming centuries under RCP8.5, sea level rise is projected to exceed rates of several centimetres per year resulting in multi-metre rise (medium confidence), while for RCP2.6 sea level rise is projected to be limited to around 1m in 2300 (low confidence). Extreme sea levels and coastal hazards will be exacerbated by projected increases in tropical cyclone intensity and precipitation (high confidence). Projected changes in waves and tides vary locally in whether they amplify or ameliorate these hazards (medium confidence). {Cross-Chapter Box 5 in Chapter 1; Cross-Chapter Box 8 in Chapter 3; 4.1; 4.2; 5.2.2, 6.3.1; Figures SPM.1, SPM.4, SPM.5} B3.1 The global mean sea level (GMSL) rise under RCP2.6 is projected to be 0.39 m (0.26–0.53 m, likely range) for the period 2081–2100, and 0.43 m (0.29–0.59 m, likely range) in 2100 with respect to 1986–2005. For RCP8.5, the corresponding GMSL rise is 0.71 m (0.51–0.92 m, likely range) for 2081–2100 and 0.84 m (0.61–1.10 m, likely range) in 2100. Mean sea level rise projections are higher by 0.1 m compared to AR5 under RCP8.5 in 2100, and the likely range extends beyond 1 m in 2100 due to a larger projected ice loss from the Antarctic Ice Sheet (medium confidence). The uncertainty at the end of the century is mainly determined by the ice sheets, especially in Antarctica. {4.2.3; Figures SPM.1, SPM.5} B3.2 Sea level projections show regional differences around GMSL. Processes not driven by recent climate change, such as local subsidence caused by natural processes and human activities, are important to relative sea level changes at the coast (high confidence). While the relative importance of climate-driven sea level rise is projected to increase over time, local processes need to be considered for projections and impacts of sea level (high confidence). {SPMA3.4, 4.2.1, 4.2.2, Figure SPM.5}. B3.3 The rate of global mean sea level rise is projected to reach 15 mm yr–1 (10–20 mm yr–1, likely range) under RCP8.5 in 2100, and to exceed several centimetres per year in the 22nd century. Under RCP2.6, the rate is projected to reach 4 mm yr-1 (2–6 mm yr–1, likely range) in 2100. Model studies indicate multi-meter rise in sea level by 2300 (2.3–5.4 m for RCP8.5 and 0.6–1.07 m under RCP2.6) (low confidence), indicating the importance of reduced emissions for limiting sea level rise. Processes controlling the timing of future ice-shelf loss and the extent of ice sheet instabilities could increase Antarctica’s contribution to sea level rise to values substantially higher than the likely range on century and longer time-scales (low confidence). Considering the consequences of sea level rise that a collapse of parts of the Antarctic Ice Sheet entails, this high impact risk merits attention. {Cross-Chapter Box 5 in Chapter 1, Cross-Chapter Box 8 in Chapter 3, 4.1, 4.2.3} B3.4 Global mean sea level rise will cause the frequency of extreme sea level events at most locations to increase. Local sea levels that historically occurred once per century (historical centennial events) are projected to occur at least annually at most locations by 2100 under all RCP scenarios (high confidence). Many low-lying megacities and Subject to Copyedit SPM-23 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere small islands (including SIDS) are projected to experience historical centennial events at least annually by 2050 under RCP2.6, RCP4.5 and RCP8.5. The year when the historical centennial event becomes an annual event in the mid-latitudes occurs soonest in RCP8.5, next in RCP4.5 and latest in RCP2.6. The increasing frequency of high water levels can have severe impacts in many locations depending on the level of exposure (high confidence). {4.2.3; 6.3; Figures SPM.4, SPM.5} B3.5 Significant wave heights (the average height from trough to crest of the highest one-third of waves) are projected to increase across the Southern Ocean and tropical eastern Pacific (high confidence) and Baltic Sea (medium confidence) and decrease over the North Atlantic and Mediterranean Sea under RCP8.5 (high confidence). Coastal tidal amplitudes and patterns are projected to change due to sea level rise and coastal adaptation measures (very likely). Projected changes in waves arising from changes in weather patterns, and changes in tides due to sea level rise, can locally enhance or ameliorate coastal hazards (medium confidence). {6.3.1, 5.2.2} B3.6 The average intensity of tropical cyclones, the proportion of Category 4 and 5 tropical cyclones and the associated average precipitation rates are projected to increase for a 2°C global temperature rise above any baseline period (medium confidence). Rising mean sea levels will contribute to higher extreme sea levels associated with tropical cyclones (very high confidence). Coastal hazards will be exacerbated by an increase in the average intensity, magnitude of storm surge and precipitation rates of tropical cyclones. There are greater increases projected under RCP8.5 than under RCP2.6 from around mid-century to 2100 (medium confidence). There is low confidence in changes in the future frequency of tropical cyclones at the global scale. {6.3.1} Projected Risks for Ecosystems B.4 Future land cryosphere changes will continue to alter terrestrial and freshwater ecosystems in high-mountain and polar regions with major shifts in species distributions resulting in changes in ecosystem structure and functioning, and eventual loss of globally unique biodiversity (medium confidence). Wildfire is projected to increase significantly for the rest of this century across most tundra and boreal regions, and also in some mountain regions (medium confidence). {2.3.3, Box 3.4, 3.4.3} B4.1 In high-mountain regions, further upslope migration by lower-elevation species, range contractions, and increased mortality will lead to population declines of many alpine species, especially glacier- or snowdependent species (high confidence), with local and eventual global species loss (medium confidence). The persistence of alpine species and sustaining ecosystem services depends on appropriate conservation and adaptation measures (high confidence). {2.3.3} Subject to Copyedit SPM-24 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere B4.2 On Arctic land, a loss of globally unique biodiversity is projected as limited refugia exist for some High-Arctic species and hence they are outcompeted by more temperate species (medium confidence). Woody shrubs and trees are projected to expand to cover 24–52% of Arctic tundra by 2050 (medium confidence). The boreal forest is projected to expand at its northern edge, while diminishing at its southern edge where it is replaced by lower biomass woodland/shrublands (medium confidence). {3.4.3, Box 3.4} B4.3 Permafrost thaw and decrease in snow will affect Arctic and mountain hydrology and wildfire, with impacts on vegetation and wildlife (medium confidence). About 20% of Arctic land permafrost is vulnerable to abrupt permafrost thaw and ground subsidence, which is projected to increase small lake area by over 50% by 2100 for RCP8.5 (medium confidence). Even as the overall regional water cycle is projected to intensify, including increased precipitation, evapotranspiration, and river discharge to the Arctic Ocean, decreases in snow and permafrost may lead to soil drying with consequences for ecosystem productivity and disturbances (medium confidence). Wildfire is projected to increase for the rest of this century across most tundra and boreal regions, and also in some mountain regions, while interactions between climate and shifting vegetation will influence future fire intensity and frequency (medium confidence). {2.3.3, 3.4.1, 3.4.2, 3.4.3, SPM B1} B5. A decrease in global biomass of marine animal communities, their production, and fisheries catch potential, and a shift in species composition are projected over the 21st century in ocean ecosystems from the surface to the deep seafloor under all emission scenarios (medium confidence). The rate and magnitude of decline are projected to be highest in the tropics (high confidence), whereas impacts remain diverse in polar regions (medium confidence) and increase for high emission scenarios. Ocean acidification (medium confidence), oxygen loss (medium confidence) and reduced sea ice extent (medium confidence) as well as non-climatic human activities (medium confidence) have the potential to exacerbate these warming-induced ecosystem impacts. {3.2.3, 3.3.3, 5.2.2, 5.2.3, 5.2.4, 5.4.1, Figure SPM.3} B5.1 Projected ocean warming and changes in net primary production alter biomass, production and community structure of marine ecosystems. The global-scale biomass of marine animals across the foodweb is projected to decrease by 15.0 ± 5.9% (very likely range) and the maximum catch potential of fisheries by 20.5–24.1% by the end of the 21st century relative to 1986–2005 under RCP8.5 (medium confidence). These changes are projected to be very likely three to four times larger under RCP8.5 than RCP2.6. {3.2.3, 3.3.3, 5.2.2, 5.2.3, 5.4.1, Figure SPM.3}. B5.2 Under enhanced stratification reduced nutrient supply is projected to cause tropical ocean net primary production to decline by 7–16% (very likely range) for RCP8.5 by 2081–2100 (medium confidence). In tropical regions, marine animal biomass and production are projected to decrease more than the global average under all emissions scenarios in the 21st century (high confidence). Warming and sea ice changes are projected to increase marine net primary production in the Arctic (medium confidence) and around Antarctica (low confidence), modified by changing Subject to Copyedit SPM-25 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere nutrient supply due to shifts in upwelling and stratification. Globally, the sinking flux of organic matter from the upper ocean is projected to decrease, linked largely due to changes in net primary production (high confidence). As a result, 95% or more of the deep sea (3000–6000 m depth) seafloor area and cold-water coral ecosystems are projected to experience declines in benthic biomass under RCP8.5 (medium confidence) {3.2.3, 5.2.2. 5.2.4, Figure SPM.1} B5.3 Warming, ocean acidification, reduced seasonal sea ice extent and continued loss of multi-year sea ice are projected to impact polar marine ecosystems through direct and indirect effects on habitats, populations and their viability (medium confidence). The geographical range of Arctic marine species, including marine mammals, birds and fish is projected to contract, while the range of some sub-Arctic fish communities is projected to expand, further increasing pressure on high-Arctic species (medium confidence). In the Southern Ocean, the habitat of Antarctic krill, a key prey species for penguins, seals and whales, is projected to contract southwards under both RCP2.6 and RCP8.5 (medium confidence). {3.2.2, 3.2.3, 5.2.3} B5.4 Ocean warming, oxygen loss, acidification and a decrease in flux of organic carbon from the surface to the deep ocean are projected to harm habitat-forming cold-water corals, which support high biodiversity, partly through decreased calcification, increased dissolution of skeletons, and bioerosion (medium confidence). Vulnerability and risks are highest where and when temperature and oxygen conditions both reach values outside species’ tolerance ranges (medium confidence). {Box 5.2, Figure SPM.3} Subject to Copyedit SPM-26 Total pages: 42 APPROVED SPM Subject to Copyedit IPCC SR Ocean and Cryosphere SPM-27 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere Figure SPM.3: Projected changes, impacts and risks for ocean regions and ecosystems: a) depth integrated net primary production (NPP from CMIP52727), b) total animal biomass (depth integrated, including fishes and invertebrates from FISHMIP28), c) maximum fisheries catch potential and d) impacts and risks for coastal and open ocean ecosystems. The three left panels represent the simulated (a,b) and observed (c) mean values for the recent past (1986–2005), the middle and right panels represent projected changes (%) by 2081–2100 relative to recent past under low (RCP2.6) and high (RCP8.5) greenhouse gas emissions scenario {Box SPM.1}, respectively. Total animal biomass in the recent past (b, left panel) represents the projected total animal biomass by each spatial pixel relative to the global average. c) *Average observed fisheries catch in the recent past (based on data from the Sea Around Us global fisheries database); projected changes in maximum fisheries catch potential in shelf seas are based on the average outputs from two fisheries and marine ecosystem models. To indicate areas of model inconsistency, shaded areas represent regions where models disagree in the direction of change for more than: a) and b) 3 out of 10 model projections, and c) one out of two models. Although unshaded, the projected change in the Arctic and Antarctic regions in b) total animal biomass and c) fisheries catch potential have low confidence due to uncertainties associated with modelling multiple interacting drivers and ecosystem responses. Projections presented in b) and c) are driven by changes in ocean physical and biogeochemical conditions e.g., temperature, oxygen level, and net primary production projected from CMIP5 Earth system models. **The epipelagic refers to the uppermost part of the ocean with depth <200 m from the surface where there is enough sunlight to allow photosynthesis. d) Assessment of risks for coastal and open ocean ecosystems based on observed and projected climate impacts on ecosystem structure, functioning and biodiversity. Impacts and risks are shown in relation to changes in Global Mean Surface Temperature (GMST) relative to pre-industrial level. Since assessments of risks and impacts are based on global mean Sea Surface Temperature (SST), the corresponding SST levels are shown.29 The assessment of risk transitions is described in Chapter 5 Sections 5.2, 5.3, 5.2.5 and 5.3.7 and Supplementary Materials SM5.3, TableSM5.6, TableSM5.8 and other parts of the underlying report. The figure indicates assessed risks at approximate warming levels and increasing climate-related hazards in the ocean: ocean warming, acidification, deoxygenation, increased density stratification, changes in carbon fluxes, sea level rise, and increased frequency and/or intensity of extreme events. The assessment considers the natural adaptive capacity of the ecosystems, their exposure and vulnerability. Impact and risk levels do not consider risk reduction strategies such as human interventions, or future changes in non-climatic drivers. Risks for ecosystems were assessed by considering biological, biogeochemical, geomorphological and physical aspects. Higher risks associated with compound effects of climate hazards include habitat and biodiversity loss, changes in species composition and distribution ranges, and impacts/risks on ecosystem structure and functioning, including changes in animal/plant biomass and density, productivity, carbon fluxes, and sediment transport. As part of the assessment, literature was compiled and data extracted into a summary table. A multi-round expert elicitation process was undertaken with independent evaluation of threshold judgement, and a final consensus discussion. Further information on methods and underlying literature can be found in Chapter 5, Sections 5.2 and 5.3 and Supplementary Material. {3.2.3, 3.2.4, 5.2, 5.3, 5.2.5, 5.3.7, SM5.6, SM5.8, Figure 5.16, Cross Chapter Box 1 in Chapter 1 Table CCB1} 27 NPP is estimated from the Coupled Models Intercomparison Project 5 (CMIP5). 28 Total animal biomass is from the Fisheries and Marine Ecosystem Models Intercomparison Project (FISHMIP). 29 The conversion between GMST and SST is based on a scaling factor of 1.44 derived from changes in an ensemble of RCP8.5 simulations; this scaling factor has an uncertainty of about 4 % due to differences between the RCP2.6 and RCP8.5 scenarios {Table SPM.1}. Subject to Copyedit SPM-28 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere B6. Risks of severe impacts on biodiversity, structure and function of coastal ecosystems are projected to be higher for elevated temperatures under high compared to low emissions scenarios in the 21st century and beyond. Projected ecosystem responses include losses of species habitat and diversity, and degradation of ecosystem functions. The capacity of organisms and ecosystems to adjust and adapt is higher at lower emissions scenarios (high confidence). For sensitive ecosystems such as seagrass meadows and kelp forests, high risks are projected if global warming exceeds 2°C above pre-industrial temperature, combined with other climate-related hazards (high confidence). Warm water corals are at high risk already and are projected to transition to very high risk even if global warming is limited to 1.5°C (very high confidence). {4.3.3, 5.3, 5.5, Figure SPM.3} B6.1 All coastal ecosystems assessed are projected to face increasing risk level, from moderate to high risk under RCP2.6 to high to very high risk under RCP8.5 by 2100. Intertidal rocky shore ecosystems are projected to be at very high risk by 2100 under RCP8.5 (medium confidence) due to exposure to warming, especially during marine heatwaves, as well as to acidification, sea level rise, loss of calcifying species and biodiversity (high confidence). Ocean acidification challenges these ecosystems and further limits their habitat suitability (medium confidence) by inhibiting recovery through reduced calcification and enhanced bioerosion. The decline of kelp forests is projected to continue in temperate regions due to warming, particularly under the projected intensification of marine heatwaves, with high risk of local extinctions under RCP8.5 (medium confidence). {5.3, 5.3.5, 5.3.6, 5.3.7, 6.4.2, Figure SPM.3} B6.2 Seagrass meadows and saltmarshes and associated carbon stores are at moderate risk at 1.5°C global warming and increase with further warming (medium confidence). Globally, 20–90% of current coastal wetlands are projected to be lost by 2100, depending on projected sea level rise, regional differences and wetland types, especially where vertical growth is already constrained by reduced sediment supply and landward migration is constrained by steep topography or human modification of shorelines (high confidence). {4.3.3, 5.3.2, Figure SPM.3, SPM A6.1} B6.3 Ocean warming, sea level rise and tidal changes are projected to expand salinization and hypoxia in estuaries (high confidence) with high risks for some biota leading to migration, reduced survival, and local extinction under high emission scenarios (medium confidence). These impacts are projected to be more pronounced in more vulnerable eutrophic and shallow estuaries with low tidal range in temperate and high latitude regions (medium confidence). {5.2.2., 5.3.1, Figure SPM.3} B6.4 Almost all warm-water coral reefs are projected to suffer significant losses of area and local extinctions, even if global warming is limited to 1.5°C (high confidence). The species composition and diversity of remaining reef communities is projected to differ from present-day reefs (very high confidence). {5.3.4, 5.4.1, Figure SPM.3}. Subject to Copyedit SPM-29 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere Projected Risks for People and Ecosystem Services B7. Future cryosphere changes on land are projected to affect water resources and their uses, such as hydropower (high confidence) and irrigated agriculture in and downstream of high-mountain areas (medium confidence), as well as livelihoods in the Arctic (medium confidence). Changes in floods, avalanches, landslides, and ground destabilization are projected to increase risk for infrastructure, cultural, tourism, and recreational assets (medium confidence). {2.3, 2.3.1, 3.4.3} B7.1 Disaster risks to human settlements and livelihood options in high mountain areas and the Arctic are expected to increase (medium confidence), due to future changes in hazards such as floods, fires, landslides, avalanches, unreliable ice and snow conditions, and increased exposure of people and infrastructure (high confidence). Current engineered risk reduction approaches are projected to be less effective as hazards change in character (medium confidence). Significant risk reduction and adaptation strategies help avoid increased impacts from mountain flood and landslide hazards as exposure and vulnerability are increasing in many mountain regions during this century (high confidence).{2.3.2, 3.4.3, 3.5.2} B7.2 Permafrost thaw-induced subsidence of the land surface is projected to impact overlying urban and rural communication and transportation infrastructure in the Arctic and in high mountain areas (medium confidence). The majority of Arctic infrastructure is located in regions where permafrost thaw is projected to intensify by mid-century. Retrofitting and redesigning infrastructure has the potential to halve the costs arising from permafrost thaw and related climate-change impacts by 2100 (medium confidence). {2.3.4, 3.4.1, 3.4.3} B7.3 High mountain tourism, recreation and cultural assets are projected to be negatively affected by future cryospheric changes (high confidence). Current snowmaking technologies are projected to be less effective in reducing risks to ski tourism in a warmer climate in most parts of Europe, North America, and Japan, in particular at 2°C global warming and beyond (high confidence). {2.3.5, 2.3.6} B8. Future shifts in fish distribution and decreases in their abundance and fisheries catch potential due to climate change are projected to affect income, livelihoods, and food security of marine resource-dependent communities (medium confidence). Long-term loss and degradation of marine ecosystems compromises the ocean’s role in cultural, recreational, and intrinsic values important for human identity and well-being (medium confidence). {3.2.4, 3.4.3, 5.4.1, 5.4.2, 6.4} B8.1 Projected geographical shifts and decreases of global marine animal biomass and fish catch potential are more pronounced under RCP8.5 relative to RCP2.6 elevating the risk for income and livelihoods of dependent human communities, particularly in areas that are economically vulnerable (medium confidence). The projected Subject to Copyedit SPM-30 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere redistribution of resources and abundance increases the risk of conflicts among fisheries, authorities or communities (medium confidence). Challenges to fisheries governance are widespread under RCP8.5 with regional hotspots such as the Arctic and tropical Pacific Ocean (medium confidence). {3.5.2, 5.4.1, 5.4.2, 5.5.2, 5.5.3, 6.4.2, Figure SPM.3} B8.2 The decline in warm water coral reefs is projected to greatly compromise the services they provide to society, such as food provision (high confidence), coastal protection (high confidence) and tourism (medium confidence). Increases in the risks for seafood security (medium confidence) associated with decreases in seafood availability are projected to elevate the risk to nutritional health in some communities highly dependent on seafood (medium confidence), such as those in the Arctic, West Africa, and Small Island Developing States. Such impacts compound any risks from other shifts in diets and food systems caused by social and economic changes and climate change over land (medium confidence). {3.4.3, 5.4.2, 6.4.2} B8.3 Global warming compromises seafood safety (medium confidence) through human exposure to elevated bioaccumulation of persistent organic pollutants and mercury in marine plants and animals (medium confidence), increasing prevalence of waterborne Vibrio pathogens (medium confidence), and heightened likelihood of harmful algal blooms (medium confidence). These risks are projected to be particularly large for human communities with high consumption of seafood, including coastal Indigenous communities (medium confidence), and for economic sectors such as fisheries, aquaculture, and tourism (high confidence). {3.4.3, 5.4.2, Box 5.3} B8.4 Climate change impacts on marine ecosystems and their services put key cultural dimensions of lives and livelihoods at risk (medium confidence), including through shifts in the distribution or abundance of harvested species and diminished access to fishing or hunting areas. This includes potentially rapid and irreversible loss of culture and local knowledge and Indigenous knowledge, and negative impacts on traditional diets and food security, aesthetic aspects, and marine recreational activities (medium confidence). {3.4.3, 3.5.3, 5.4.2} B9. Increased mean and extreme sea level, alongside ocean warming and acidification, are projected to exacerbate risks for human communities in low-lying coastal areas (high confidence). In Arctic human communities without rapid land uplift, and in urban atoll islands, risks are projected to be moderate to high even under a low emissions scenario (RCP2.6) (medium confidence), including reaching adaptation limits (high confidence). Under a high emissions scenario (RCP8.5), delta regions and resource rich coastal cities are projected to experience moderate to high risk levels after 2050 under current adaptation (medium confidence). Ambitious adaptation including transformative governance is expected to reduce risk (high confidence), but with context-specific benefits. {4.3.3, 4.3.4, 6.9.2, Cross-chapter Box 9, SM4.3, Figure SPM.5} B9.1 In the absence of more ambitious adaptation efforts compared to today, and under current trends of increasing exposure and vulnerability of coastal communities, risks, such as erosion and land loss, flooding, salinization, Subject to Copyedit SPM-31 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere and cascading impacts due to mean sea level rise and extreme events are projected to significantly increase throughout this century under all greenhouse gas emissions scenarios (very high confidence). Under the same assumptions, annual coastal flood damages are projected to increase by 2–3 orders of magnitude by 2100 compared to today (high confidence). {4.3.3; 4.3.4; Box 6.1; 6.8; SM4.3; Figures SPM.4, SPM.5} B9.2 High to very high risks are approached for vulnerable communities in coral reef environments, urban atoll islands and low-lying Arctic locations from sea level rise well before the end of this century in case of high emissions scenarios. This entails adaptation limits being reached, which are the points at which an actor’s objectives (or system needs) cannot be secured from intolerable risks through adaptive actions (high confidence). Reaching adaptation limits (e.g., biophysical, geographical, financial, technical, social, political, and institutional) depends on the emissions scenario and context-specific risk tolerance, and is projected to expand to more areas beyond 2100, due to the long-term commitment of sea level rise (medium confidence). Some island nations are likely to become uninhabitable due to climaterelated ocean and cryosphere change (medium confidence), but habitability thresholds remain extremely difficult to assess. {4.3.4, 4.4.2, 4.4.3, 5.5.2, Cross-Chapter Box 9, SM4.3, SPM C1, Glossary, Figure SPM.5} B9.3 Globally, a slower rate of climate-related ocean and cryosphere change provides greater adaptation opportunities (high confidence). While there is high confidence that ambitious adaptation, including governance for transformative change, has the potential to reduce risks in many locations, such benefits can vary between locations. At global scale, coastal protection can reduce flood risk by 2–3 orders of magnitude during the 21st century, but depends on investments on the order of tens to several hundreds of billions of US$ per year (high confidence). While such investments are generally cost efficient for densely populated urban areas, rural and poorer areas may be challenged to afford such investments with relative annual costs for some small island states amounting to several percent of GDP (high confidence). Even with major adaptation efforts, residual risks and associated losses are projected to occur (medium confidence), but context-specific limits to adaptation and residual risks remain difficult to assess. {4.1.3, 4.2.2.4, 4.3.1, 4.3.2, 4.3.4., 4.4.3, 6.9.1, 6.9.2, Cross-Chapter Boxes 1–2 in Chapter 1, SM4.3, Figure SPM.5} Subject to Copyedit SPM-32 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere Figure SPM.4: The effect of regional sea-level rise on extreme sea level events at coastal locations. a) Schematic illustration of extreme sea level events and their average recurrence in the recent past (1986–2005) and the future. As a consequence of mean sea level rise, local sea levels that historically occurred once per century (historical centennial events, HCEs) are projected to recur more frequently in the future. b) The year in which HCEs are expected to recur once per year on average under RCP8.5 and RCP2.6, at the 439 individual coastal locations where the observational record is sufficient. The absence of a circle indicates an inability to perform an assessment due to a lack of data but does not indicate absence of exposure and risk. The darker the circle, the earlier this transition is expected. The likely range is ±10 years for locations where this transition is expected before 2100. White circles (33% of locations under RCP2.6 and 10% under RCP8.5) indicate that HCEs are not expected to recur once per year before 2100. c) An indication at which locations this transition of HCEs to annual events is projected to occur more than 10 years later under RCP2.6 compared to RCP8.5. As the scenarios lead to small differences by 2050 in many locations results are not shown here for RCP4.5 but they are available in Chapter 4. {4.2.3, Figure 4.10, Figure 4.12} Subject to Copyedit SPM-33 Total pages: 42 APPROVED SPM SPM.C IPCC SR Ocean and Cryosphere IMPLEMENTING RESPONSES TO OCEAN AND CRYOSPHERE CHANGE Challenges C1. Impacts of climate-related changes in the ocean and cryosphere increasingly challenge current governance efforts to develop and implement adaptation responses from local to global scales, and in some cases pushing them to their limits. People with the highest exposure and vulnerability are often those with lowest capacity to respond (high confidence). {1.5, 1.7, Cross-Chapter Boxes 2–3 of Chapter 1, 2.3.1, 2.3.2, 2.3.3, 2.4, 3.2.4, 3.4.3, 3.5.2, 3.5.3, 4.1, 4.3.3, 4.4.3, 5.5.2, 5.5.3, 6.9} C1.1 The temporal scales of climate change impacts in ocean and cryosphere and their societal consequences operate on time horizons which are longer than those of governance arrangements (e.g., planning cycles, public and corporate decision making cycles, and financial instruments). Such temporal differences challenge the ability of societies to adequately prepare for and respond to long-term changes including shifts in the frequency and intensity of extreme events (high confidence). Examples include changing landslides and floods in high mountain regions and risks to important species and ecosystems in the Arctic, as well as to low-lying nations and islands, small island nations, other coastal regions and to coral reef ecosystems. {2.3.2, 3.5.2, 3.5.4, 4.4.3, 5.2, 5.3, 5.4, 5.5.1, 5.5.2, 5.5.3, 6.9} C1.2 Governance arrangements (e.g., marine protected areas, spatial plans and water management systems) are, in many contexts, too fragmented across administrative boundaries and sectors to provide integrated responses to the increasing and cascading risks from climate-related changes in the ocean and/or cryosphere (high confidence). The capacity of governance systems in polar and ocean regions to respond to climate change impacts has strengthened recently, but this development is not sufficiently rapid or robust to adequately address the scale of increasing projected risks (high confidence). In high mountains, coastal regions and small islands, there are also difficulties in coordinating climate adaptation responses, due to the many interactions of climatic and non-climatic risk drivers (such as inaccessibility, demographic and settlement trends, or land subsidence caused by local activities) across scales, sectors and policy domains (high confidence). {2.3.1, 3.5.3, 4.4.3, 5.4.2, 5.5.2, 5.5.3, Box 5.6, 6.9, Cross-Chapter Box 3 in Chapter 1} C1.3 There are a broad range of identified barriers and limits for adaptation to climate change in ecosystems (high confidence). Limitations include the space that ecosystems require, non-climatic drivers and human impacts that need to be addressed as part of the adaptation response, the lowering of adaptive capacity of ecosystems because of climate change, and the slower ecosystem recovery rates relative to the recurrence of climate impacts, availability of technology, knowledge and financial support, and existing governance arrangements (medium confidence). {3.5.4, 5.5.2} Subject to Copyedit SPM-34 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere C1.4 Financial, technological, institutional and other barriers exist for implementing responses to current and projected negative impacts of climate-related changes in the ocean and cryosphere, impeding resilience building and risk reduction measures (high confidence). Whether such barriers reduce adaptation effectiveness or correspond to adaptation limits depends on context specific circumstances, the rate and scale of climate changes and on the ability of societies to turn their adaptive capacity into effective adaptation responses. Adaptive capacity continues to differ between as well as within communities and societies (high confidence). People with highest exposure and vulnerability to current and future hazards from ocean and cryosphere changes are often also those with lowest adaptive capacity, particularly in low-lying islands and coasts, Arctic and high mountain regions with development challenges (high confidence). {2.3.1, 2.3.2, 2.3.7, Box 2.4, 3.5.2, 4.3.4, 4.4.2, 4.4.3, 5.5.2, 6.9, Cross-Chapter Boxes 2 and 3 in Chapter 1, Cross-Chapter Box 9} Strengthening Response Options C2. The far-reaching services and options provided by ocean and cryosphere-related ecosystems can be supported by protection, restoration, precautionary ecosystem-based management of renewable resource use, and the reduction of pollution and other stressors (high confidence). Integrated water management (medium confidence) and ecosystem-based adaptation (high confidence) approaches lower climate risks locally and provide multiple societal benefits. However, ecological, financial, institutional and governance constraints for such actions exist (high confidence), and in many contexts ecosystem-based adaptation will only be effective under the lowest levels of warming (high confidence). {2.3.1, 2.3.3, 3.2.4, 3.5.2, 3.5.4, 4.4.2, 5.2.2, 5.4.2, 5.5.1, 5.5.2, Figure SPM.5} C2.1 Networks of protected areas help maintain ecosystem services, including carbon uptake and storage, and enable future ecosystem-based adaptation options by facilitating the poleward and altitudinal movements of species, populations, and ecosystems that occur in response to warming and sea level rise (medium confidence). Geographic barriers, ecosystem degradation, habitat fragmentation and barriers to regional cooperation limit the potential for such networks to support future species range shifts in marine, high mountain and polar land regions. (high confidence). {2.3.3, 3.2.3, 3.3.2, 3.5.4, 5.5.2, Box 3.4} C2.2 Terrestrial and marine habitat restoration, and ecosystem management tools such as assisted species relocation and coral gardening, can be locally effective in enhancing ecosystem-based adaptation (high confidence). Such actions are most successful when they are community-supported, are science-based whilst also using local knowledge and Indigenous knowledge, have long-term support that includes the reduction or removal of nonclimatic stressors, and under the lowest levels of warming (high confidence). For example, coral reef restoration options may be ineffective if global warming exceeds 1.5°C, because corals are already at high risk (very high confidence) at current levels of warming. {2.3.3, 4.4.2, 5.3.7, 5.5.1, 5.5.2, Box 5.5, Fig SPM.3} Subject to Copyedit SPM-35 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere C2.3 Strengthening precautionary approaches, such as rebuilding overexploited or depleted fisheries, and responsiveness of existing fisheries management strategies reduces negative climate change impacts on fisheries, with benefits for regional economies and livelihoods (medium confidence). Fisheries management that regularly assesses and updates measures over time, informed by assessments of future ecosystem trends, reduces risks for fisheries (medium confidence) but has limited ability to address ecosystem change. {3.2.4, 3.5.2, 5.4.2, 5.5.2, 5.5.3, Figure SPM.5} C2.4 Restoration of vegetated coastal ecosystems, such as mangroves, tidal marshes and seagrass meadows (coastal ‘blue carbon’ ecosystems), could provide climate change mitigation through increased carbon uptake and storage of around 0.5% of current global emissions annually (medium confidence). Improved protection and management can reduce carbon emissions from these ecosystems. Together, these actions also have multiple other benefits, such as providing storm protection, improving water quality, and benefiting biodiversity and fisheries (high confidence). Improving the quantification of carbon storage and greenhouse gas fluxes of these coastal ecosystems will reduce current uncertainties around measurement, reporting and verification (high confidence). {Box 4.3, 5.4, 5.5.1, 5.5.2, Annex I: Glossary} C2.5 Ocean renewable energy can support climate change mitigation, and can comprise energy extraction from offshore winds, tides, waves, thermal and salinity gradient and algal biofuels. The emerging demand for alternative energy sources is expected to generate economic opportunities for the ocean renewable energy sector (high confidence), although their potential may also be affected by climate change (low confidence). {5.4.2, 5.5.1, Figure 5.23} C2.6 Integrated water management approaches across multiple scales can be effective at addressing impacts and leveraging opportunities from cryosphere changes in high mountain areas. These approaches also support water resource management through the development and optimization of multi-purpose storage and release of water from reservoirs (medium confidence), with consideration of potentially negative impacts to ecosystems and communities. Diversification of tourism activities throughout the year supports adaptation in high mountain economies (medium confidence). {2.3.1, 2.3.5} C3. Coastal communities face challenging choices in crafting context-specific and integrated responses to sea level rise that balance costs, benefits and trade-offs of available options and that can be adjusted over time (high confidence). All types of options, including protection, accommodation, ecosystem-based adaptation, coastal advance and retreat, wherever possible, can play important roles in such integrated responses (high confidence). {4.4.2, 4.4.3, 4.4.4, 6.9.1, Cross-Chapter Box 9; Figure SPM.5} Subject to Copyedit SPM-36 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere C3.1. The higher the sea levels rise, the more challenging is coastal protection, mainly due to economic, financial and social barriers rather than due to technical limits (high confidence). In the coming decades, reducing local drivers of exposure and vulnerability such as coastal urbanization and human-induced subsidence constitute effective responses (high confidence). Where space is limited, and the value of exposed assets is high (e.g., in cities), hard protection (e.g., dikes) is likely to be a cost-efficient response option during the 21st century taking into account the specifics of the context (high confidence), but resource-limited areas may not be able to afford such investments. Where space is available, ecosystem-based adaptation can reduce coastal risk and provide multiple other benefits such as carbon storage, improved water quality, biodiversity conservation and livelihood support (medium confidence). {4.3.2, 4.4.2, Box 4.1, Cross-Chapter Box 9, Figure SPM.5} C3.2 Some coastal accommodation measures, such as early warning systems and flood-proofing of buildings, are often both low cost and highly cost-efficient under current sea levels (high confidence). Under projected sea level rise and increase in coastal hazards some of these measures become less effective unless combined with other measures (high confidence). All types of options, including protection, accommodation, ecosystem-based adaptation, coastal advance and planned relocation, if alternative localities are available, can play important roles in such integrated responses (high confidence). Where the community affected is small, or in the aftermath of a disaster, reducing risk by coastal planned relocations is worth considering if safe alternative localities are available. Such planned relocation can be socially, culturally, financially and politically constrained (very high confidence). {4.4.2, Box 4.1, Cross-Chapter Box 9, SPM B3} C3.3 Responses to sea-level rise and associated risk reduction present society with profound governance challenges, resulting from the uncertainty about the magnitude and rate of future sea level rise, vexing trade-offs between societal goals (e.g., safety, conservation, economic development, intra- and inter-generational equity), limited resources, and conflicting interests and values among diverse stakeholders (high confidence). These challenges can be eased using locally appropriate combinations of decision analysis, land-use planning, public participation, diverse knowledge systems and conflict resolution approaches that are adjusted over time as circumstances change (high confidence). {Cross-Chapter Box 5 in Chapter 1, 4.4.3, 4.4.4, 6.9} C3.4 Despite the large uncertainties about the magnitude and rate of post 2050 sea level rise, many coastal decisions with time horizons of decades to over a century are being made now (e.g., critical infrastructure, coastal protection works, city planning) and can be improved by taking relative sea-level rise into account, favouring flexible responses (i.e., those that can be adapted over time) supported by monitoring systems for early warning signals, periodically adjusting decisions (i.e., adaptive decision making), using robust decision-making approaches, expert judgement, scenario-building, and multiple knowledge systems (high confidence). The sea level rise range that needs to be considered for planning and implementing coastal responses depends on the risk tolerance of stakeholders. Subject to Copyedit SPM-37 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere Stakeholders with higher risk tolerance (e.g., those planning for investments that can be very easily adapted to unforeseen conditions) often prefer to use the likely range of projections, while stakeholders with a lower risk tolerance (e.g., those deciding on critical infrastructure) also consider global and local mean sea level above the upper end of the likely range (globally 1.1 m under RCP8.5 by 2100) and from methods characterised by lower confidence such as from expert elicitation. {1.8.1, 1.9.2, 4.2.3, 4.4.4, Figure 4.2, Cross-Chapter Box 5 in Chapter 1, Figure SPM.5, SPM B3} Subject to Copyedit SPM-38 Total pages: 42 APPROVED SPM Subject to Copyedit IPCC SR Ocean and Cryosphere SPM-39 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere Figure SPM.5: Sea level rise risks and responses. The term response is used here instead of adaptation because some responses, such as retreat, may or may not be considered to be adaptation. Panel a) shows the combined risk of coastal flooding, erosion and salinization for illustrative geographies in 2100, due to changing mean and extreme sea levels under RCP2.6 and RCP8.5 and under two response scenarios. Risks under RCPs 4.5 and 6.0 were not assessed due to a lack of literature for the assessed geographies. The assessment does not account for changes in extreme sea level beyond those directly induced by mean sea level rise; risk levels could increase if other changes in extreme sea levels were considered (e.g., due to changes in cyclone intensity). Panel a) considers a socioeconomic scenario with relatively stable coastal population density over the century {SM4.3.2}. Risks to illustrative geographies have been assessed based on relative sea-level changes projected for a set of specific examples: New York City, Shanghai and Rotterdam for resource-rich coastal cities covering a wide range of response experiences; South Tarawa, Fongafale and Male’ for urban atoll islands; Mekong and Ganges-Brahmaputra-Meghna for large tropical agricultural deltas; and Bykovskiy, Shishmaref, Kivalina, Tuktoyaktuk and Shingle Point for Arctic communities located in regions remote from rapid glacio-isostatic adjustment {4.2, 4.3.4, SM4.2}. The assessment distinguishes between two contrasting response scenarios. “No-to-moderate response” describes efforts as of today (i.e., no further significant action or new types of actions). “Maximum potential response” represents a combination of responses implemented to their full extent and thus significant additional efforts compared to today, assuming minimal financial, social and political barriers. The assessment has been conducted for each sea level rise and response scenario, as indicated by the burning embers in the figure; in-between risk levels are interpolated {4.3.3}. The assessment criteria include exposure and vulnerability (density of assets, level of degradation of terrestrial and marine buffer ecosystems), coastal hazards (flooding, shoreline erosion, salinization), in-situ responses (hard engineered coastal defenses, ecosystem restoration or creation of new natural buffers areas, and subsidence management) and planned relocation. Planned relocation refers to managed retreat or resettlement as described in Chapter 4, i.e., proactive and local-scale measures to reduce risk by relocating people, assets and infrastructure. Forced displacement is not considered in this assessment. Panel a) also highlights the relative contributions of in-situ responses and planned relocation to the total risk reduction. Panel b) schematically illustrates the risk reduction (vertical arrows) and risk delay (horizontal arrows) through mitigation and/or responses to sea level rise. Panel c) summarizes and assesses responses to sea level rise in terms of their effectiveness, costs, co-benefits, drawbacks, economic efficiency and associated governance challenges {4.4.2}. Panel d) presents generic steps of an adaptive decision-making approach, as well as key enabling conditions for responses to sea level rise {4.4.4; 4.4.5}. Enabling Conditions C4. Enabling climate resilience and sustainable development depends critically on urgent and ambitious emissions reductions coupled with coordinated sustained and increasingly ambitious adaptation actions (very high confidence). Key enablers for implementing effective responses to climate-related changes in the ocean and cryosphere include intensifying Subject to Copyedit SPM-40 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere cooperation and coordination among governing authorities across spatial scales and planning horizons. Education and climate literacy, monitoring and forecasting, use of all available knowledge sources, sharing of data, information and knowledge, finance, addressing social vulnerability and equity, and institutional support are also essential. Such investments enable capacity-building, social learning, and participation in context-specific adaptation, as well as the negotiation of trade-offs and realisation of co-benefits in reducing short-term risks and building long-term resilience and sustainability. (high confidence) This report reflects the state of science for ocean and cryosphere for low levels of global warming (1.5°C), as also assessed in earlier IPCC and IPBES reports. {1.1, 1.5, 1.8.3, 2.3.1, 2.3.2, 2.4, Figure 2.7, 2.5, 3.5.2, 3.5.4, 4.4, 5.2.2, Box 5.3, 5.4.2, 5.5.2, 6.4.3, 6.5.3, 6.8, 6.9, Cross-Chapter Box 9, Figure SPM.5} C4.1 In light of observed and projected changes in the ocean and cryosphere, many nations will face challenges to adapt, even with ambitious mitigation (very high confidence). In a high emissions scenario, many oceanand cryosphere-dependent communities are projected to face adaptation limits (e.g. biophysical, geographical, financial, technical, social, political and institutional) during the second half of the 21st century. Low emission pathways, for comparison, limit the risks from ocean and cryosphere changes in this century and beyond and enable more effective responses (high confidence), whilst also creating co-benefits. Profound economic and institutional transformative change will enable Climate Resilient Development Pathways in the ocean and cryosphere context (high confidence). {1.1, 1.4– 1.7, Cross-Chapter Boxes 1–3 in Chapter 1, 2.3.1, 2.4, Box 3.2, Figure 3.4, Cross-Chapter Box 7 in Chapter 3, 3.4.3, 4.2.2, 4.2.3, 4.3.4, 4.4.2, 4.4.3, 4.4.6, 5.4.2, 5.5.3, 6.9.2, Cross-Chapter Box 9, Figure SPM.5} C4.2 Intensifying cooperation and coordination among governing authorities across scales, jurisdictions, sectors, policy domains and planning horizons can enable effective responses to changes in the ocean, cryosphere and to sea level rise (high confidence). Regional cooperation, including treaties and conventions, can support adaptation action; however, the extent to which responding to impacts and losses arising from changes in the ocean and cryosphere is enabled through regional policy frameworks is currently limited (high confidence). Institutional arrangements that provide strong multiscale linkages with local and Indigenous communities benefit adaptation (high confidence). Coordination and complementarity between national and transboundary regional policies can support efforts to address risks to resource security and management, such as water and fisheries (medium confidence). {2.3.1, 2.3.2, 2.4, Box 2.4, 2.5, 3.5.2, 3.5.3, 3.5.4, 4.4.4, 4.4.5, Table 4.9, 5.5.2, 6.9.2} C4.3 Experience to date – for example, in responding to sea level rise, water-related risks in some high mountains, and climate change risks in the Arctic – also reveal the enabling influence of taking a long-term perspective when making short-term decisions, explicitly accounting for uncertainty of context-specific risks beyond 2050 (high confidence), and building governance capabilities to tackle complex risks (medium confidence). {2.3.1, 3.5.4, 4.4.4, 4.4.5, Table 4.9, 5.5.2, 6.9, Figure SPM.5} Subject to Copyedit SPM-41 Total pages: 42 APPROVED SPM IPCC SR Ocean and Cryosphere C4.4 Investments in education and capacity building at various levels and scales facilitates social learning and long-term capability for context-specific responses to reduce risk and enhance resilience (high confidence). Specific activities include utilization of multiple knowledge systems and regional climate information into decision making, and the engagement of local communities, Indigenous peoples, and relevant stakeholders in adaptive governance arrangements and planning frameworks (medium confidence). Promotion of climate literacy and drawing on local, Indigenous and scientific knowledge systems enables public awareness, understanding and social learning about localityspecific risk and response potential (high confidence). Such investments can develop, and in many cases transform existing institutions and enable informed, interactive and adaptive governance arrangements (high confidence). {1.8.3, 2.3.2, Figure 2.7, Box 2.4, 2.4, 3.5.2, 3.5.4, 4.4.4, 4.4.5, Table 4.9, 5.5.2, 6.9} C4.5 Context-specific monitoring and forecasting of changes in the ocean and the cryosphere informs adaptation planning and implementation, and facilitates robust decisions on trade-offs between short- and long-term gains (medium confidence). Sustained long-term monitoring, sharing of data, information and knowledge and improved context-specific forecasts, including early warning systems to predict more extreme El Niño/La Niña events, tropical cyclones, and marine heatwaves, help to manage negative impacts from ocean changes such as losses in fisheries, and adverse impacts on human health, food security, agriculture, coral reefs, aquaculture, wildfire, tourism, conservation, drought and flood (high confidence). {2.4, 2.5, 3.5.2, 4.4.4, 5.5.2, 6.3.1, 6.3.3, 6.4.3, 6.5.3, 6.9} C4.6 Prioritising measures to address social vulnerability and equity underpins efforts to promote fair and just climate resilience and sustainable development (high confidence), and can be helped by creating safe community settings for meaningful public participation, deliberation and conflict resolution (medium confidence). {Box 2.4, 4.4.4, 4.4.5, Table 4.9, Figure SPM.5} C4.7 This assessment of the ocean and cryosphere in a changing climate reveals the benefits of ambitious mitigation and effective adaptation for sustainable development and, conversely, the escalating costs and risks of delayed action. The potential to chart Climate Resilient Development Pathways varies within and among ocean, high mountain and polar land regions. Realising this potential depends on transformative change. This highlights the urgency of prioritising timely, ambitious, coordinated and enduring action. (very high confidence) {1.1, 1.8, Cross-Chapter Box 1, 2.3, 2.4, 3.5, 4.2.1, 4.2.2, 4.3.4, 4.4, Table 4.9, 5.5, 6.9, Cross-Chapter Box 9, Figure SPM.5} Subject to Copyedit SPM-42 Total pages: 42 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Chapter 1: Framing and Context of the Report Coordinating Lead Authors: Nerilie Abram (Australia), Jean-Pierre Gattuso (France), Anjal Prakash (Nepal/India) Lead Authors: Lijing Cheng (China), Maria Paz Chidichimo (Argentina), Susan Crate (USA), Hiroyuki Enomoto (Japan), Matthias Garschagen (Germany), Nicolas Gruber (Switzerland), Sherilee Harper (Canada), Elisabeth Holland (Fiji), Raphael Martin Kudela (USA), Jake Rice (Canada), Konrad Steffen (Switzerland), Karina von Schuckmann (France) Contributing Authors: Nathaniel Bindoff (Australia), Sinead Collins (UK), Rebecca Colvin (Australia), Daniel Farinotti (Switzerland), Nathalie Hilmi (France/Monaco), Jochen Hinkel (Switzerland), Regine Hock (USA), Alexandre Magnan (France), Michael Meredith (UK), Avash Pandey (Nepal), Mandira Singh Shrestha (Nepal), Anna Sinisalo (Nepal/Finland), Catherine Sutherland (South Africa), Phillip Williamson (UK) Review Editors: Monika Rhein (Germany), David Schoeman (Australia) Chapter Scientists: Avash Pandey (Nepal), Bethany Ellis (Australia) Date of Draft: 14 June 2019 Notes: TSU Compiled Version Table of Contents Executive Summary ................................................................................................................................... 3 1.1 Why this Special Report?................................................................................................................... 6 Box 1.1: Major Components and Characteristics of the Ocean and Cryosphere .................................... 7 1.2 Role of the Ocean and Cryosphere in the Earth System ................................................................... 9 1.2.1 Ocean and Cryosphere in Earth’s Energy, Water and Biogeochemical Cycles ........................... 9 1.2.2 Interactions Between the Ocean and Cryosphere ..................................................................... 10 1.3 Timescales, Thresholds and Detection of Ocean and Cryosphere Change..................................... 11 1.4 Changes in the Ocean and Cryosphere............................................................................................ 13 1.4.1 Observed and Projected Changes in the Ocean ....................................................................... 14 1.4.2 Observed and Projected Changes in the Cryosphere................................................................ 14 Cross Chapter Box 1: Scenarios, Pathways and Reference Periods ....................................................... 15 1.5 Risk and Impacts Related to Ocean and Cryosphere Change ........................................................ 18 Cross-Chapter Box 2: Key Concepts of Risk, Adaptation, Resilience and Transformation.................. 19 1.5.1 Hazards and Opportunities for Natural Systems, Ecosystems, and Human Systems .................. 22 1.5.2 Exposure of Natural Systems, Ecosystems, and Human Systems ............................................... 23 1.5.3 Vulnerabilities in Natural Systems, Ecosystems, and Human Systems ...................................... 24 1.6 Addressing the Causes and Consequences of Climate Change for the Ocean and Cryosphere .... 25 1.6.1 Mitigation and Adaptation Options in the Ocean and Cryosphere............................................ 25 1.6.2 Adaptation in Natural Systems, Ecosystems, and Human Systems ............................................ 26 1.7 Governance and Institutions ............................................................................................................ 28 Cross-Chapter Box 3: Governance of the Ocean, Coasts and the Cryosphere under Climate Change 28 1.8 Knowledge Systems for Understanding and Responding to Change .............................................. 32 1.8.1 Scientific Knowledge ............................................................................................................... 33 1.8.2 Indigenous Knowledge and Local Knowledge .......................................................................... 35 Cross-Chapter Box 4: Indigenous Knowledge and Local Knowledge in Ocean and Cryosphere Change ..................................................................................................................................................... 36 1.8.3 The Role of Knowledge in People’s Responses to Climate, Ocean and Cryosphere Change .... 40 1.9 Approaches Taken in this Special Report ....................................................................................... 40 1.9.1 Methodologies Relevant to this Report..................................................................................... 40 Subject to Copyedit 1-1 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere 1.9.2 Communication of Confidence in Assessment Findings ............................................................ 41 Cross-Chapter Box 5: Confidence and Deep Uncertainty ...................................................................... 43 1.10 Integrated Storyline of this Special Report ..................................................................................... 45 FAQ 1.1: How do changes in the ocean and cryosphere affect our life on planet Earth?...................... 48 References ................................................................................................................................................ 53 Subject to Copyedit 1-2 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Executive Summary This special report assesses new knowledge since the IPCC 5th Assessment Report (AR5) and the Special Report on Global Warming of 1.5°C (SR1.5) on how the ocean and cryosphere have and are expected to change with ongoing global warming, the risks and opportunities these changes bring to ecosystems and people, and mitigation, adaptation and governance options for reducing future risks. Chapter 1 provides context on the importance of the ocean and cryosphere, and the framework for the assessments in subsequent chapters of the report. All people on Earth depend directly or indirectly on the ocean and cryosphere. The fundamental roles of the ocean and cryosphere in the Earth system include the uptake and redistribution of anthropogenic carbon dioxide and heat by the ocean, as well as their crucial involvement of in the hydrological cycle. The cryosphere also amplifies climate changes through snow, ice and permafrost feedbacks. Services provided to people by the ocean and/or cryosphere include food and freshwater, renewable energy, health and wellbeing, cultural values, trade, and transport. {1.1, 1.2, 1.5} Sustainable development is at risk from emerging and intensifying ocean and cryosphere changes. Ocean and cryosphere changes interact with each of the United Nations Sustainable Development Goals (SDGs). Progress on climate action (SDG13) would reduce risks to aspects of sustainable development that are fundamentally linked to the ocean and cryosphere and the services they provide (high confidence1). Progress on achieving the SDGs can contribute to reducing the exposure or vulnerabilities of people and communities to the risks of ocean and cryosphere change (medium confidence). {1.1} Communities living in close connection with polar, mountain, and coastal environments are particularly exposed to the current and future hazards of ocean and cryosphere change. Coasts are home to approximately 28% of the global population, including around 11% living on land less than 10 m above sea level. Almost 10% of the global population lives in the Arctic or high mountain regions. People in these regions face the greatest exposure to ocean and cryosphere change, and poor and marginalised people here are particularly vulnerable to climate-related hazards and risks (very high confidence). The adaptive capacity of people, communities and nations is shaped by social, political, cultural, economic, technological, institutional, geographical, and demographic factors. {1.1, 1.5, 1.6, Cross-Chapter Box 2 in Chapter 1} Ocean and cryosphere changes are pervasive and observed from high mountains, to the polar regions, to coasts, and into the deep ocean. AR5 assessed that the ocean is warming (0-700 m: virtually certain2; 700-2000 m: likely), sea level is rising (high confidence), and ocean acidity is increasing (high confidence). Most glaciers are shrinking (high confidence), the Greenland and Antarctic ice sheets are losing mass (high confidence), sea-ice extent in the Arctic is decreasing (very high confidence), Northern Hemisphere snow cover is decreasing (very high confidence), and permafrost temperatures are increasing (high confidence). Improvements since AR5 in observation systems, techniques, reconstructions and model developments, have advanced scientific characterisation and understanding of ocean and cryosphere change, including in previously identified areas of concern such as ice sheets and Atlantic Meridional Overturning Circulation. {1.1, 1.4, 1.8.1} Evidence and understanding of the human causes of climate warming, and of associated ocean and cryosphere changes, has increased over the past 30 years of IPCC assessments (very high confidence). Human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial 1 In this Report, the following summary terms are used to describe the available evidence: limited, medium, or robust; and for the degree of agreement: low, medium, or high. A level of confidence is expressed using five qualifiers: very low, low, medium, high, and very high, and typeset in italics, e.g., medium confidence. For a given evidence and agreement statement, different confidence levels can be assigned, but increasing levels of evidence and degrees of agreement are correlated with increasing confidence (see Section 1.9.2 and Figure 1.4 for more details). 2 In this Report, the following terms have been used to indicate the assessed likelihood of an outcome or a result: Virtually certain 99–100% probability, Very likely 90–100%, Likely 66–100%, About as likely as not 33–66%, Unlikely 0–33%, Very unlikely 0–10%, and Exceptionally unlikely 0–1%. Additional terms (Extremely likely: 95– 100%, More likely than not >50–100%, and Extremely unlikely 0–5%) may also be used when appropriate. Assessed likelihood is typeset in italics, e.g., very likely (see Section 1.9.2 and Figure 1.4 for more details). This Report also uses the term ‘likely range’ to indicate that the assessed likelihood of an outcome lies within the 17-83% probability range. Subject to Copyedit 1-3 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere levels (SR1.5). Areas of concern in earlier IPCC reports, such as the expected acceleration of sea level rise, are now observed (high confidence). Evidence for expected slow-down of Atlantic Meridional Overturning Circulation is emerging in sustained observations and from long-term palaeoclimate reconstructions (medium confidence), and may be related with anthropogenic forcing according to model simulations, although this remains to be properly attributed. Significant sea level rise contributions from Antarctic ice sheet mass loss (very high confidence), which earlier reports did not expect to manifest this century, are already being observed. {1.1, 1.4} Ocean and cryosphere changes and risks by the end-of-century (2081-2100) will be larger under high greenhouse gas emission scenarios, compared with low emission scenarios (very high confidence). Projections and assessments of future climate, ocean and cryosphere changes in SROCC are commonly based on coordinated climate model experiments from the Coupled Model Intercomparison Project Phase 5 (CMIP5) forced with Representative Concentration Pathways (RCPs) of future radiative forcing. Current emissions continue to grow at a rate consistent with a high emission future without effective climate change mitigation policies (referred to as RCP8.5). The SROCC assessment contrasts this high greenhouse gas emission future with a low greenhouse gas emission, high mitigation future (referred to as RCP2.6) that gives a two in three chance of limiting warming by the end of the century to less than 2oC above preindustrial. {Cross-Chapter Box 1 in Chapter 1} Characteristics of ocean and cryosphere change include thresholds of abrupt change, long-term changes that cannot be avoided, and irreversibility (high confidence). Ocean warming, acidification and deoxygenation, ice sheet and glacier mass loss, and permafrost degradation are expected to be irreversible on timescales relevant to human societies and ecosystems. Long response times of decades to millennia mean that the ocean and cryosphere are committed to long-term change even after atmospheric greenhouse gas concentrations and radiative forcing stabilise (high confidence). Ice melt or the thawing of permafrost involve thresholds (state changes) that allow for abrupt, nonlinear responses to ongoing climate warming (high confidence). These characteristics of ocean and cryosphere change pose risks and challenges to adaptation {1.1, Box 1.1, 1.3}. Societies will be exposed, and challenged to adapt, to changes in the ocean and cryosphere even if current and future efforts to reduce greenhouse gas emissions keep global warming well below 2°C (very high confidence). Ocean and cryosphere-related mitigation and adaptation measures include options that address the causes of climate change, support biological and ecological adaptation, or enhance societal adaptation. Most ocean-based local mitigation and adaptation measures have limited effectiveness to mitigate climate change and reduce its consequences at the global scale, but are useful to implement because they address local risks, often have co-benefits such as biodiversity conservation, and have few adverse side effects. Effective mitigation at a global scale will reduce the need and cost of adaptation, and reduce the risks of surpassing limits to adaptation. Ocean-based carbon dioxide removal at the global scale has potentially large negative ecosystem consequences. {Cross-Chapter Box 2 in Chapter 1, 1.6.1, 1.6.2} The scale and cross-boundary dimensions of changes in the ocean and cryosphere challenge the ability of communities, cultures and nations to respond effectively within existing governance frameworks (high confidence). Profound economic and institutional transformations are needed if climate-resilient development is to be achieved (high confidence). Changes in the ocean and cryosphere, the ecosystem services that they provide, the drivers of those changes, and the risks to marine, coastal, polar and mountain ecosystems, occur on spatial and temporal scales that may not align within existing governance structures and practices (medium confidence). This report highlights the requirements for transformative governance, international and transboundary cooperation, and greater empowerment of local communities in the governance of the ocean, coasts, and cryosphere in a changing climate. {1.5, 1.7, Cross-Chapter Box 2 in Chapter 1, Cross-Chapter Box 3 in Chapter 1} Robust assessments of ocean and cryosphere change, and the development of context-specific governance and response options, depend on utilising and strengthening all available knowledge systems (high confidence). Scientific knowledge from observations, models and syntheses provides global to local scale understandings of climate change (very high confidence). Indigenous knowledge and local knowledge provide context-specific and socio-culturally relevant understandings for effective responses and Subject to Copyedit 1-4 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere policies (medium confidence). Education and climate literacy enable climate action and adaptation (high confidence). {1.8, Cross-Chapter Box 4 in Chapter 1} Long-term sustained observations and continued modeling are critical for detecting, understanding and predicting ocean and cryosphere change, providing the knowledge to inform risk assessments and adaptation planning (high confidence). Knowledge gaps exist in scientific knowledge for important regions, parameters and processes of ocean and cryosphere change, including for physically plausible, high impact changes like high-end sea level rise scenarios that would be costly if realised without effective adaptation planning and even then may exceed limits to adaptation. Means such as expert judgement, scenario-building, and invoking multiple lines of evidence enable comprehensive risk assessments even in cases of uncertain future ocean and cryosphere changes. {1.8.1, 1.9.2; Cross-Chapter Box 5 in Chapter 1} Subject to Copyedit 1-5 Total pages: 72 FINAL DRAFT 1.1 Chapter 1 IPCC SR Ocean and Cryosphere Why this Special Report? All people depend directly or indirectly on the ocean and cryosphere (see FAQ1.1). Coasts are the most densely populated areas on Earth. As of 2010, 28% of the global population (1.9 billion people) were living in areas less than 100 km from the coastline and less than 100 m above sea level, including 17 major cities which are each home to more than 5 million people (Kummu et al., 2016). The low elevation coastal zone (land less than 10 m above sea level), where people and infrastructure are most exposed to coastal hazards, is currently home to around 11% of the global population (around 680 million people), and by 2050 the population in this zone is projected to grow to more than one billion under all shared socio-economic pathways (Section 4.3.3.2; Merkens et al., 2016; O’Neill et al., 2017). In 2010, approximately 4 million people lived in the Arctic (Section 3.5.1), and an increase of only 4% is projected for 2030 (Heleniak, 2014) compared to 16 to 23% for the global population increase (O’Neill et al., 2017). Almost 10% of the global population (around 670 million people) lived in high mountain regions in 2010, and by 2050 the population in these regions is expected to grow to between 736 to 844 million across the shared socio-economic pathways (Section 2.1). For people living in close contact with the ocean and cryosphere, these systems provide essential livelihoods, food security, well-being and cultural identity, but are also a source of hazards (Sections 1.5.1, 1.5.2). Even people living far from the ocean or cryosphere depend on these systems. Snow and glacier melt from high mountains helps to sustain the rivers that deliver water resources to downstream populations (Kaser et al., 2010; Sharma et al., 2019). In the Indus and Ganges river basins, for example, snow and glacier melt provides enough water to grow food crops to sustain a balanced diet for 38 million people, and supports the livelihoods of 129 million farmers (Biemans et al., 2019). The ocean and cryosphere regulate global climate and weather; the ocean is the primary source of rain and snowfall needed to sustain life on land, and uptake of heat and carbon into the ocean has so far limited the magnitude of anthropogenic warming experienced at the Earth’s surface (Section 1.2). The ocean’s biosphere is responsible for about half of the primary production on Earth, and around 17% of the non-grain protein in human diets is derived from the ocean (FAO, 2018). Ocean and cryosphere changes can result in differing consequences and benefits on local to global scales; for example, declining sea ice in the Arctic is allowing access to shorter international shipping routes but restricting traditional sea-ice based travel for Arctic communities. Human activities are estimated to have so far caused approximately 1°C of global warming (0.8-1.2°C likely range; above pre-industrial levels; IPCC, 2018). The IPCC Fifth Assessment Report (AR5) concluded that, ‘Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased’ (IPCC, 2013). Subsequently, Parties to the Paris Agreement aimed to strengthen the global response to the threats of climate change, including by ‘holding the increase in global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C’ (UNFCCC, 2015). Pervasive ocean and cryosphere changes that are already being caused by human-induced climate change are observed from high mountains, to the polar regions, to coasts and into the deep reaches of the ocean. Changes by the end of this century are expected to be larger under high greenhouse gas emission futures compared with low emission futures (Cross-Chapter Box 1 in Chapter 1), and inaction on reducing emissions will have large economic costs. If human impacts on the ocean continue unabated, declines in ocean health and services are projected to cost the global economy $428 billion per year by 2050, and $1.979 trillion per year by 2100. Alternatively, steps to reduce these impacts could save more than a trillion dollars per year by 2100 (Ackerman, 2013). Similarly, sea level rise scenarios of 25 to 123 cm by 2100 without adaptation are expected to see 0.2 to 4.6% of the global population impacted by coastal flooding annually, with average annual losses amounting to 0.3 to 9.3% of global GDP. Investment in adaptation reduces by 2 to 3 orders of magnitude the number of people flooded and the losses caused (Hinkel et al., 2014). The United Nations 2030 Sustainable Development Goals (SDGs) (UN, 2015) are all connected to varying extents with the ocean and cryosphere (see FAQ1.2). Climate action (SDG13) would limit future ocean and cryosphere changes (high confidence; Cross-Chapter Box 1 in Chapter 1, Figure 1.5, Chapter 2-6), and would reduce risks to SDGs that are fundamentally linked to the ocean and cryosphere, including life below Subject to Copyedit 1-6 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere water, and clean water and sanitation. (Sections 2.4, 4.4, 5.4; Szabo et al., 2016; LeBlanc et al., 2017; Singh et al., 2018; Visbeck, 2018; Wymann von Dach et al., 2018; Kulonen, Accepted). Other goals for sustainable development depend on the services the ocean and cryosphere provide or are impacted by ocean and cryosphere change; including, life on land, health and wellbeing, eradicating poverty and hunger, economic growth, clean energy, infrastructure, and sustainable cities and communities. Progress on the other SDGs (education, gender equality, reduced inequalities, responsible consumption, strong institutions, and partnerships for the goals) are important for reducing the vulnerability of people and communities to the risks of ocean and cryosphere changes (Section 1.5; 2.3), and for supporting mitigation and adaptation responses (Sections 1.6, 1.7 and 1.8.3; medium confidence). The characteristics of ocean and cryosphere change (Section 1.3) present particular challenges to climateresilient development pathways. Ocean acidification and deoxygenation, ice sheet and glacier mass loss, and permafrost degradation are expected to be irreversible on timescales relevant to human societies and ecosystems (Lenton et al., 2008; Solomon et al., 2009; Frölicher and Joos, 2010; Cai et al., 2016; Kopp et al., 2016). Ocean and cryosphere changes also have the potential to worsen anthropogenic climate change, globally and regionally; for example, by additional greenhouse gas emissions released through permafrost thaw that would intensify anthropogenic climate change globally, or by increasing the absorption of solar radiation through snow and ice loss in the Arctic that is causing regional climate to warm at more than twice the global rate (AMAP, 2017; Steffen et al., 2018). Ocean and cryosphere changes place particular pressures on the adaptive capacities of cultures who maintain centuries to millennia-old relationships to the planet’s polar, mountain, and coastal environments, as well as on cities, states and nations whose territorial boundaries are being transformed by ongoing sea level rise (Gerrard and Wannier, 2013). The scale and cross-boundary dimensions of changes in the ocean and cryosphere challenge the ability of current local, regional, to international governance structures to respond (Section 1.7). Profound economic and institutional transformations are needed if climate-resilient development is to be achieved, including ambitious mitigation efforts to avoid the risks of large-scale and abrupt ocean and cryosphere changes. The commissioning of this Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) recognises the interconnected ways in which the ocean and cryosphere are expected to change in a warming climate. SROCC assesses new knowledge since AR5 and provides an integrated approach across IPCC working groups I and II, linking physical changes with their ecological and human impacts, and the strategies to respond and adapt to future risks. It is one of three special reports being produced by the IPCC during its Sixth Assessment Cycle (in addition to the three working groups’ main assessment reports). The concurrent IPCC Special Report on Climate Change and Land (SRCCL; due August 2019) links to SROCC where terrestrial environments and their habitability interact closely with the ocean or cryosphere, such as in mountain, Arctic, and coastal regions. The recent IPCC Special Report on Global Warming of 1.5°C (SR1.5) concluded that human-induced warming will reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate (high confidence), and that there are widespread benefits to human and natural systems of limiting warming to 1.5oC compared with 2oC or more (high confidence; IPCC, 2018). [START BOX 1.1 HERE] Box 1.1: Major Components and Characteristics of the Ocean and Cryosphere Ocean The global ocean is the interconnected body of saline water that encompasses polar to equatorial climate zones and covers 71% of the Earth surface. It includes the Arctic, Pacific, Atlantic, Indian, and Southern oceans, as well as their marginal seas. The ocean contains about 97% of the Earth’s water, supplies 99% of the Earth's biologically-habitable space, and provides roughly half of the primary production on Earth. Coasts are where ocean and land processes interact, and includes coastal cities, deltas, estuaries, and other coastal ecosystems such as mangrove forests. Low elevation coastal zones (less than 10 m above sea level) are densely populated and particularly exposed to hazards from the ocean (Chapters 4 to 6, Cross-Chapter Box 9). Moving into the ocean, the continental shelf represents the shallow ocean areas (depth <200 m) that surround continents and islands, before the seafloor descends at the continental slope into the deep ocean. The edge of the continental shelf is often used to identify the coastal ocean from the open ocean. Ocean Subject to Copyedit 1-7 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere depth and distance from the coast may influence the governance and economic access that applies to ocean areas (Cross-Chapter Box 3 in Chapter 1). The average depth of the global ocean is about 3700 m, with a maximum depth of more than 10,000 m. The ocean is vertically stratified with less dense water sitting above more dense layers, determined by the seawater temperature, salinity and pressure. The surface of the ocean is in direct contact with the atmosphere, except for sea ice covered regions. Sunlight penetrates the water column and supports primary production (by phytoplankton) down to 50 to 200 m depth (epipelagic zone). Atmospheric-driven mixing occurs from the sea surface and into the mesopelagic zone (200 to 1000 m). The distinction between the upper ocean and deep ocean depends on the processes being considered. The ocean is a fundamental climate regulator on seasonal to millennial time scales. Seawater has a heat capacity four times larger than air and holds vast quantities of dissolved carbon. Heat, water, and biogeochemically relevant gases (e.g., oxygen (O2) and carbon dioxide (CO2)) exchange at the air-sea interface, and ocean currents and mixing caused by winds, tides, wave dynamics, density differences, and turbulence redistribute these throughout the global ocean (Box 1.1, Figure 1). Cryosphere The cryosphere refers to frozen components of the Earth system that are at or below the land and ocean surface. These include snow, glaciers, ice sheets, ice shelves, icebergs, sea ice, lake ice, river ice, permafrost and seasonally frozen ground. Cryosphere is widespread in polar regions (Chapter 3) and high mountains (Chapter 2), and changes in the cryosphere can have far-reaching and even global impacts (Chapters 2 to 6, Cross-Chapter Box 9). Snow is common in polar and mountain regions. It can ultimately either melt seasonally, or transform into ice layers that build glaciers and ice sheets. Snow feeds groundwater and river runoff together with glacier melt, causes natural hazards (avalanches, rain-on-snow flood events), and is a critical economic resource for hydropower and tourism. Snow plays a major role in maintaining high mountain and Arctic ecosystems, affects the Earth’s energy budget by reflecting solar radiation (albedo effect), and influences the temperature of underlying permafrost. Ice sheets and glaciers are land-based ice, built up by accumulating snowfall on their surface. Presently, around 10% of Earth’s land area is covered by glaciers or ice sheets, which in total hold about 69% of Earth’s freshwater (Gleick, 1996). Ice sheets and glaciers flow, and at their margins ice and/or meltwater is discharged into lakes, rivers or the ocean. The largest ice bodies on Earth are the Greenland and Antarctic ice sheets. Marine-based sections of ice sheets (e.g., West Antarctic Ice Sheet) sit upon bedrock that largely lies below sea level and are in contact with ocean heat, making them vulnerable to rapid and irreversible ice loss. Ice sheets and glaciers that lose more ice than they accumulate contribute to global sea level rise. Ice shelves are extensions of ice sheets and glaciers that float in the surrounding ocean. The transition between the grounded part of an ice sheet and a floating ice shelf is called the grounding line. Changes in ice-shelf size do not directly contribute to sea level rise, but buttressing of ice shelves restrict the flow of land-based ice past the grounding line into the ocean. Sea ice forms from freezing of seawater, and sea ice on the ocean surface is further thickened by snow accumulation. Sea ice may be discontinuous pieces moved on the ocean surface by wind and currents (pack ice), or a motionless sheet attached to the coast or to ice shelves (fast ice). Sea ice provides many critical functions: it provides essential habitat for polar species and supports the livelihoods of people in the Arctic (including Indigenous peoples); regulates climate by reflecting solar radiation; inhibits ocean-atmosphere exchange of heat, momentum, and gases (including CO2); supports global deep ocean circulation via dense (cold and salty) water formation; and aids or hinders transportation and travel routes in the polar regions. Permafrost is ground (soil or rock containing ice and frozen organic material) that remains at or below 0°C for at least two consecutive years. It occurs on land in polar and high-mountain areas, and also as submarine permafrost in shallow parts of the Arctic and Southern oceans. Permafrost thickness ranges from less than 1 m to greater than 1000 m. It usually occurs beneath an active layer, which thaws and freezes annually. Unlike glaciers and snow, the spatial distribution and temporal changes of permafrost cannot easily be Subject to Copyedit 1-8 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere observed. Permafrost thaw can cause hazards, including ground subsidence or landslides, and influence global climate through emissions of greenhouse gases from microbial breakdown of previously frozen organic carbon. Box 1.1, Figure 1: Schematic illustration of key components and changes of the ocean and cryosphere, and their linkages in the Earth system through the movement of heat, water, and carbon (Section 1.2). Climate change-related effects in the ocean include sea level rise, increasing ocean heat content and marine heat waves, ocean deoxygenation, and ocean acidification (Section 1.4.1). Changes in the cryosphere include the decline of Arctic sea ice extent, Antarctic and Greenland ice sheet mass loss, glacier mass loss, permafrost thaw, and decreasing snow cover extent (Section 1.4.2). For illustration purposes, a few examples of where humans directly interact with ocean and cryosphere are shown. [END BOX 1.1 HERE] 1.2 1.2.1 Role of the Ocean and Cryosphere in the Earth System Ocean and Cryosphere in Earth’s Energy, Water and Biogeochemical Cycles The ocean and cryosphere play a key role in the Earth system. Powered by the Sun’s energy, large quantities of energy, water, and biogeochemical elements (predominantly carbon, nitrogen, oxygen, and hydrogen) are exchanged between all components of the Earth system, including between the ocean and cryosphere (Box 1.1, Figure 1). During an equilibrium (stable) climate state, the amount of incoming solar energy is balanced by an equal amount of outgoing radiation at the top of Earth’s atmosphere (Hansen et al., 2011). At the Earth’s surface energy from the sun is transformed into various forms (heat, potential, latent, kinetic, and chemical), that drive weather systems in the atmosphere and currents in the ocean, fuel photosynthesis on land and in the ocean, and fundamentally determine the climate (Trenberth et al., 2014). The ocean has a large capacity to store and release heat, and the Earth’s energy budget can be effectively monitored through the heat content of the ocean on time scales longer than one year (Palmer and McNeall, 2014; von Schuckmann et al., 2016; Cheng et al., 2018). The large heat capacity of the ocean leads to different characteristics of the ocean response to external forcings compared with the atmosphere (Sections 1.3, 1.4). The reflective properties of snow and ice also play an important role in regulating climate, via the albedo effect. Increased amounts of Subject to Copyedit 1-9 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere solar energy are absorbed when snow or ice are replaced by less reflective land or ocean surfaces, resulting in a climate change feedback responsible for amplified changes. Water is exchanged between the ocean, the atmosphere, the land, and the cryosphere as part of the hydrological cycle driven by solar heating (Box 1.1, Figure 1; Trenberth et al., 2007; Lagerloef et al., 2010; Durack et al., 2016). Evaporation from the surface ocean is the main source of water in the atmosphere, which is moved back to the Earth’s surface as precipitation (Gimeno et al., 2012). The hydrological cycle is closed by the eventual return of water to the ocean by rivers, streams, and groundwater flow, and through ice discharge and melting of ice sheets and glaciers (Yu, 2018). Hydrological extremes related to the ocean include floods from extreme rainfall (including tropical cyclones) or ocean circulation-related droughts (Sections 6.3, 6.5), while cryosphere-related flooding can be caused by rapid snow melt and meltwater discharge events (Sections 2.3, 3.4). Ninety-two percent of the carbon on Earth that is not locked up in geological reservoirs (e.g., in sedimentary rocks or coal, oil and gas reservoirs) resides in the ocean (Sarmiento and Gruber, 2002). Most of this is in the form of dissolved inorganic carbon, some of which readily exchanges with CO2 in the overlying atmosphere. This represents a major control on atmospheric CO2 and makes the ocean and its carbon cycle one of the most important climate regulators in the Earth system, especially on timescales of a few hundred years and more (Sigman and Boyle, 2000; Berner and Kothavala, 2001). The ocean also contains as much organic carbon (mostly in the form of dissolved organic matter) as the total vegetation on land (Jiao et al., 2010; Hansell, 2013). Primary production in the ocean, which is as large as that on land (Field et al., 1998), fuels complex food-webs that provide essential food for people. Ocean circulation and mixing redistribute heat and carbon over large distances and depths (Delworth et al., 2017). The ocean moves heat laterally from the tropics towards polar regions (Rhines et al., 2008). Vertical redistribution of heat and carbon occurs where warm, low-density surface ocean waters transform into cool high-density waters that sink to deeper layers of the ocean (Talley, 2013), taking high carbon concentrations with them (Gruber et al., 2019). Driven by winds, ocean circulation also brings cold water up from deep layers (upwelling) in some regions, allowing heat, oxygen and carbon exchange between the deep ocean and the atmosphere (Oschlies et al., 2018; Shi et al., 2018) and fuelling biological production (Sarmiento and Gruber, 2006). 1.2.2 Interactions Between the Ocean and Cryosphere The ocean and cryosphere are interconnected in a multitude of ways (Box 1.1, Figure 1). Evaporation from the ocean provides snowfall that builds and sustains the ice sheets and glaciers that store large amounts of frozen water on land (Section 4.2.1). The vast ice sheets in Antarctica and Greenland currently hold about 66 metres of potential global sea level rise (Fretwell et al., 2013), although the loss of a large fraction of this potential would require millennia of ice sheet retreat. Ocean temperature and sea level affect ice sheet, glacier and ice-shelf stability in places where the base of ice bodies are in direct contact with ocean water (Section 3.3.1). The non-linear response of ice melt to ocean temperature changes means that even slight increases in ocean temperature have the potential to rapidly melt and destabilise large sections of an ice sheet or ice shelf (Section 3.3.1.5). The formation of sea ice leads to the production of dense ocean water that contributes to the deep ocean circulation (Section 3.3.3.2). Paleoclimate evidence and modeling indicates that releases of large amounts of glacier and ice sheet meltwater into the surface ocean can disrupt deep overturning circulation of the ocean, causing global climate impacts (Knutti et al., 2004; Golledge et al., 2019). Ice sheet meltwater in the Antarctic may cause changes in surface ocean salinity, stratification and circulation, that feedback to generate further ocean-driven melting of marine-based ice sheets (Golledge et al., 2019) and promote sea ice formation (Purich et al., 2018). The cryosphere and ocean further link through the movement of biogeochemical nutrients. For example, iron accumulated in sea ice during winter is released to the ocean during the spring and summer melt, helping to fuel ocean productivity in the seasonal sea ice zone (Tagliabue et al., 2017). Nutrient-rich sediments delivered by glaciers further connect cryosphere processes to ocean productivity (Arrigo et al., 2017). Subject to Copyedit 1-10 Total pages: 72 FINAL DRAFT 1.3 Chapter 1 IPCC SR Ocean and Cryosphere Timescales, Thresholds and Detection of Ocean and Cryosphere Change It takes hundreds of years to millennia for the entire deep ocean to turn over (Matsumoto, 2007; Gebbie and Huybers, 2012), while renewal of the large ice sheets requires many thousands of years (Huybrechts and de Wolde, 1999). Long response times mean that the deep ocean and the large ice-sheets tend to lag behind in their response to the rapidly changing climate at Earth’s surface, and that they will continue to change even after radiative forcing stabilises (e.g., Golledge et al., 2015; Figure 1.1a). Such ‘committed’ changes mean that some ocean and cryosphere changes are essentially irreversible on timescales relevant to human societies (decades to centuries), even in the presence of immediate action to limit further global warming (e.g., Section 4.2.3.5). While some aspects of the ocean and cryosphere might respond in a linear (i.e., directly proportional) manner to a perturbation by some external forcing, this may change fundamentally when critical thresholds are reached. A very important example for such a threshold is the transition from frozen water to liquid water at around 0°C that can lead to rapid acceleration of ice melt or permafrost thaw (e.g., Abram et al., 2013; Trusel et al., 2018). Such thresholds often act as tipping points, as they are associated with rapid and abrupt changes even when the underlying forcing changes gradually (Figure 1.1a, 1.1c). Tipping elements include, for example, the collapse of the ocean’s large-scale overturning circulation in the Atlantic (Section 6.7), or the collapse of the West Antarctic Ice Sheet though a process called marine ice sheet instability (CrossChapter Box 8 in Chapter 3; Lenton et al., 2008). Potential ocean and cryosphere tipping elements form part of the scientific case for efforts to limit climate warming to well below 2 oC (IPCC, 2018). Anthropogenically forced change occurs against a backdrop of substantial natural variability (Figure 1.1b). The anthropogenic signal is already detectable in global surface air temperature and several other climate variables, including ocean temperature and salinity (IPCC, 2014), but short observational records and large year-to-year variability mean that formal detection is not yet the case for many expected ocean and cryosphere changes (Jones et al., 2016). ‘Time of Emergence’ refers to the time when anthropogenic change signals emerge from the background noise of natural variability in a pre-defined reference period (Figure 1.1b; Section 5.2, Box 5.1; Hawkins and Sutton, 2012). For some variables, (e.g., for those associated with ocean acidification), the current signals emerge from this natural variability within a few decades, whereas for others, such as primary production and expected Antarctic-wide sea ice decline, the signal may not emerge for many more decades even under high emission scenarios (Collins et al., 2013; Keller et al., 2014; Rodgers et al., 2015; Frölicher et al., 2016; Jones et al., 2016). ‘Detection and Attribution’ assesses evidence for past changes in the ocean and cryosphere, relative to normal/reference-interval conditions (detection), and the extent to which these changes have been caused by anthropogenic climate change or by other factors (attribution) (Bindoff et al., 2013; Cramer et al., 2014; Knutson et al., 2017; Figure 1.1d). Reliable detection and attribution is fundamental to our understanding of the scientific basis of climate change (Hegerl et al., 2010). For example, the main attribution conclusion of the IPCC 4th Assessment Report (AR4), i.e., that “most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations”, has had a strong impact on climate policy (Petersen, 2011). In AR5 this attribution statement was elevated to “extremely likely” (Bindoff et al., 2013). Statistical approaches for attribution often involve using contrasting forcing scenarios in climate model experiments to detect the forcing that best explains an observed change (Figure 1.1d). In addition to passing the statistical test, a successful attribution also requires a firm process understanding. Confident attribution remains challenging, though, especially when there are multiple or confounding factors that influence the state of a system (Hegerl et al., 2010). Particular challenges to detection and attribution in the ocean and cryosphere include the often short observational records (Section 1.8.1.1, Figure 1.3), which are particularly confounding given the long adjustment timescales to anthropogenic forcing of many properties of interest. Extreme climate events (e.g., marine heatwaves or storm surges) push a system to near or beyond the ends of its normally observed range (Figure 1.1b; chapter 6; Seneviratne et al., 2012). Extremes can be very costly in terms of loss of life, ecosystem destruction, and economic damage. In a system affected by climate change, the recurrence and intensity of these extreme events can change much faster and have greater impacts than changes of the average system state (Easterling et al., 2000; Parmesan et al., 2000; Hughes et al., 2018). Of particular concern are ‘compound events’, when the joint probability of two or more properties of a system is Subject to Copyedit 1-11 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere extreme at the same time or closely connected in time and space (Cross-Chapter Box 5 in Chapter 1; Sections 4.3.4, 6.8). Such a compound event is given, e.g., when marine heatwaves co-occur with very low nutrient levels in the ocean potentially resulting in extreme impacts (Bond et al., 2015). The interconnectedness of the ocean and cryosphere (Section 1.2.2) can also lead to cascading effects where changes in one element trigger secondary changes in completely different but connected elements of the systems, including its socio-economic aspects. (Figure 1.1e). An example is the large change in ocean productivity triggered by the changes in circulation and iron inputs induced by the large outflow of melt waters from Greenland (Kanna et al., 2018). New methodologies for attributing extreme events, and the risks they bring to climate change have emerged since AR5 (Trenberth et al., 2015; Stott et al., 2016; KirchmeierYoung et al., 2017; Otto, 2017), especially also for the attribution of individual events through an assessment of the fraction of attributable risk (Figure 1.1f). Figure 1.1: Schematic of key concepts associated with changes in the ocean and cryosphere. (a) Differing responses of systems to gradual forcing (e.g., linear, delayed, abrupt, non-linear). (b) Evolution of a dynamical system in time, Subject to Copyedit 1-12 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere revealing both natural (unforced) variability and a response to a new (e.g., anthropogenic) forcing. Key concepts include (i) the time of emergence and (ii) extreme events near or beyond the observed range of variability. (c) Tipping points and the change of their behaviour through time in response to e.g., anthropogenic change (adapted from Lenton et al., 2008). The two minima represent two stable fixed points, separated by a maximum representing an unstable fixed point, acting as a tipping point. The ball represents the state of the system with the red dash line indicating the stability of the fixed point and the system’s response time to small perturbations. (d) Detection and attribution, i.e., the statistical framework used to determine whether a change occurs or not (detection), and whether this detected change is caused by a particular set of forcings (e.g., greenhouse gases) (attribution). (e) Cascading effects, where changes in one part of a system inevitably affect the state in another, and so forth, ultimately affecting the state of the entire system. These cascading effects can also trigger feedbacks, altering the forcing. (f) Event attribution and fraction of attributable risk. The blue (orange) probability density function shows the likelihood of the occurrence of a particular value of a climate variable of interest under natural (present = including anthropogenic forcing) conditions. The corresponding areas above the threshold indicate the probabilities Pnat and Pant of exceedance of this threshold. The fraction of attributable risk (given by FAR = 1 - Pant/Pnat ) indicates the likelihood that a particular event has occurred as a consequence of anthropogenic change (adapted from Stott et al., 2016). 1.4 Changes in the Ocean and Cryosphere Earth’s climate, ocean and cryosphere vary across a wide range of timescales. This includes the seasonal growth and melting of sea-ice, interannual variation of ocean temperature caused by the El Niño-Southern Oscillation (ENSO), to ice age cycles across tens to hundreds of thousands of years. Climate variability can arise from internally generated (i.e., unforced) fluctuations in the climate system. Variability can also occur in response to external forcings, including volcanic eruptions, changes in the Earth’s orbit around the sun, oscillations in solar activity, and changing atmospheric greenhouse gas concentrations. Since the onset of the industrial revolution, human activities have had a strong impact on the climate system, including the ocean and cryosphere. Human activities have altered the external forcings acting on Earth’s climate (Myhre et al., 2013) by changes in land use (albedo), and changes in atmospheric aerosols (e.g. soot) from the burning of biomass and fossil fuels. Most significantly, human activities have led to an accumulation of greenhouse gases (including CO2) in the atmosphere as a result of the burning of fossil fuels, cement production, agriculture, and land use change. In 2016, the global average atmospheric CO2 concentration crossed 400 parts per million, a level Earth’s atmosphere did not experience for at least the past 800,000 years and possibly much longer (Lüthi et al., 2008; Fischer et al., 2018). These anthropogenic forcings have not only warmed the ocean and begun to melt the cryosphere, but have also led to widespread biogeochemical changes driven by the oceanic uptake of anthropogenic CO2 from the atmosphere (IPCC, 2013). It is now nearly three decades since the first assessment report of the IPCC, and over that time evidence and confidence in observed and projected ocean and cryosphere changes have grown (very high confidence; Table SM1.1). Confidence in climate warming and its anthropogenic causes has increased across assessment cycles; robust detection was not yet possible in 1990, but has been characterised as unequivocal since AR4 in 2007. Projections of near-term warming rates in early reports have been realised over the subsequent decades, while projections have tended to err on the side of caution for sea level rise and ocean heat uptake that have developed faster than predicted (Brysse et al., 2013; Section 4.2, 5.2). Areas of concern in early reports which were expected but not observable are now emerging. The expected acceleration of sea level rise is now observed with high confidence (Section 4.2). There is emerging evidence in sustained observations and from long-term palaeoclimate reconstructions for the expected slow-down of Atlantic Meridional Overturning Circulation (medium confidence), although this remains to be properly attributed (Section 6.7). Significant sea level rise contributions from Antarctic ice sheet mass loss (very high confidence), which earlier reports did not expect to manifest this century, are already being observed (Section 3.3.1). Other newly emergent characteristics of ocean and cryosphere change (e.g., marine heat waves; Section 6.4) are assessed for the first time in SROCC. Subject to Copyedit 1-13 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere The IPCC Fifth Assessment Report (AR5) (IPCC, 2013; IPCC, 2014) provides ample evidence of profound and pervasive changes in the ocean and cryosphere (Sections 1.4.1, 1.4.2), and along with the recent SR1.5 report (IPCC, 2018), is the point of departure for the updated assessments made in SROCC. 1.4.1 Observed and Projected Changes in the Ocean Increasing greenhouse gases in the atmosphere cause heat uptake in the Earth system (Section 1.2) and as reported since 1970, there is high confidence3 that the majority (more than 90%) of the extra thermal energy in the Earth’s system is stored in the global ocean (IPCC, 2013). Mean ocean surface temperature has increased since the 1970s at a rate of 0.11 [0.09 to 0.13] °C per decade (high confidence), and forms part of a long-term warming of the surface ocean since the mid-19th century. The upper ocean (0-700 m, virtually certain) and intermediate ocean (700-2000 m, likely) have warmed since the 1970s. Ocean heat uptake has continued unabated since AR5 (Sections 3.2.1.2.1, 5.2), increasing the risk of marine heat waves and other extreme events (Section 6.4). During the 21st century ocean warming is projected to continue even if anthropogenic greenhouse gas emissions cease (Sections 1.3, 5.2). The global water cycle has been altered, resulting in substantial regional changes in sea surface salinity (high confidence; Rhein et al., 2013), which is expected to continue in the future (Sections 5.2.2, 6.3, 6.5). The rate of sea level rise since the mid-19th century has been larger than the mean rate of the previous two millennia (high confidence). Over the period 1901 to 2010, global mean sea level rose by 0.19 [0.17 to 0.21] m (high confidence) (Church et al., 2013; Table SM1.1). Sea level rise continues due to freshwater added to the ocean by melting of glaciers and ice sheets, and as a result of ocean expansion due to continuous ocean warming, with a projected acceleration and century to millennial-scale commitments for ongoing rise (Section 4.2.3). In SROCC, recent developments of ice-sheet modeling are assessed (Sections 1.8, 4.3, Cross-Chapter Box 8 in Chapter 3) and the projected sea level rise at the end of 21st century is higher than reported in AR5 but with a larger uncertainty range (Sections 4.2.3.2, 4.2.3.3). By 2011, the ocean had taken up about 30 ±7% of the anthropogenic CO2 that had been released to the atmosphere since the industrial revolution (Ciais et al., 2013; Section 5.2). In response, ocean pH decreased by 0.1 since the beginning of the industrial era (high confidence), corresponding to an increase in acidity of 26% (Table SM1.1) and leading to both positive and negative biological and ecological impacts (high confidence) (Gattuso et al., 2014). Evidence is increasing that the ocean’s oxygen content is declining (Oschlies et al., 2018). AR5 did not come to a final conclusion with regard to potential long-term changes in ocean productivity due to short observational records and divergent scientific evidence (Boyd et al., 2014; Section 5.2.2). Ocean acidification and deoxygenation are projected to continue over the next century with high confidence (Sections 3.2.2.3, 5.2.2). 1.4.2 Observed and Projected Changes in the Cryosphere Changes in the cryosphere documented in AR5 included the widespread retreat of glaciers (high confidence), mass loss from the Greenland and Antarctic ice sheets (high confidence), and declining extents of Arctic sea ice (very high confidence) and Northern Hemisphere spring snow cover (very high confidence; IPCC, 2013; Vaughan et al., 2013). A particularly rapid change in Earth’s cryosphere has been the decrease in Arctic sea-ice extent in all seasons (Section 3.2.1.1). AR5 assessed that there was medium confidence that a nearly-ice free summer Arctic Ocean is likely to occur before mid-century under a high emissions future (IPCC, 2013), and SR1.5 assessed that ice-free summers are projected to occur at least once per century at 1.5oC of warming, and at least once per decade at 2oC of warming above pre-industrial (IPCC, 2018). Sea ice thickness is decreasing further in the Northern Hemisphere and older ice that has survived multiple summers is rapidly disappearing; most sea ice in the Arctic is now ‘first year’ ice that grows in the autumn and winter but melts during the spring and summer (AMAP, 2017). AR5 assessed that the annual mean loss from the Greenland ice sheet very likely substantially increased from 34 [-6 to 74] Gt yr–1 (billion tonnes per year) over the period 1992 to 2001, to 215 [157 to 274] Gt yr–1 over 3 Confidence/likelihood statements in Sections 1.4.1 and 1.4.2 derived from AR5 and SR1.5, unless otherwise specified Subject to Copyedit 1-14 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere the period 2002 to 2011 (IPCC, 2013). The average rate of ice loss from the Antarctic ice sheet also likely increased from 30 [-37 to 97] Gt yr–1 over the period 1992–2001, to 147 [72 to 221] Gt yr–1 over the period 2002 to 2011 (IPCC, 2013). The average rate of ice loss from glaciers around the world (excluding glaciers on the periphery of the ice sheets), was very likely 226 [91 to 361] Gt yr-1 over the period 1971 to 2009, and 275 [140 to 410] Gt yr-1 over the period 1993 to 2009 (IPCC, 2013). The Greenland and Antarctic ice sheets are continuing to lose mass at an accelerating rate (Section 3.3) and glaciers are continuing to lose mass worldwide (Section 2.2.3, Cross-Chapter Box 6 in Chapter 2). Confidence in the quantification of glacier and ice sheet mass loss has increased across successive IPCC reports (Table SM1.1) due to the development of remote sensing observational methods (Section 1.8.1). Changes in seasonal snow are best documented for the Northern Hemisphere. AR5 reported that the extent of snow cover has decreased since the mid-20th century (very high confidence). Negative trends in both snow depth and duration are also detected with station observations (medium confidence), although results depend on elevation and observational period (Section 2.2.2). AR5 assessed that permafrost temperatures have increased in most regions since the early 1980s (high confidence), and the rate of increase has varied regionally (IPCC, 2013). Methane and carbon dioxide release from soil organic carbon is projected to continue in high mountain and polar regions (Box 2.2), and SROCC has used multiple lines of evidence to reduce uncertainty in permafrost change assessments (Cross-Chapter Box 5 in Chapter 1, Section 3.4.3.1.1). [START CROSS-CHAPTER BOX 1 HERE] Cross Chapter Box 1: Scenarios, Pathways and Reference Periods Authors: Nerilie Abram (Australia), William Cheung (Canada), Lijing Cheng (China), Thomas Frölicher (Switzerland), Mathias Hauser (Switzerland), Shengping He (Norway/China), Anne Hollowed (USA), Ben Marzeion (Germany), Samuel Morin (France), Anna Pirani (Italy), Didier Swingedouw (France) Introduction. Assessing the future risks and opportunities that climate change will bring for the ocean and cryosphere, and for their dependent ecosystems and human communities, is a main objective of this report. However, the future is inherently uncertain. A well-established methodological approach that SROCC uses to assess the future under these uncertainties is through scenario analysis (Kainuma et al., 2018). The ultimate physical driver of the ocean and cryosphere changes that SROCC assesses are greenhouse gas emissions, while the exposure to hazards and the future risks to natural and human systems are also shaped social, economic and governance factors (Cross-Chapter Box 2 in Chapter 1; Section 1.5). This CrossChapter Box introduces the main scenarios that are used in the SROCC assessment. Examples of key climate change indicators in the atmosphere and ocean projected under future greenhouse gas emission scenarios are also provided (Table CB1.1). Scenarios and pathways. Scenarios are a plausible description of how the future may develop based on a coherent and internally consistent set of assumptions about key driving forces and relationships. Pathways refer to the temporal evolution of natural and/or human systems towards a future state. In SROCC, assessments of future change frequently use climate model projections forced by pathways of future radiative forcing changes related to different socio-economic scenarios. Representative Concentration Pathways (RCPs) are a set of time series of plausible future concentrations of greenhouse gases, aerosols and chemically active gases, as well as land use changes (Moss et al., 2008; Moss et al., 2010; van Vuuren et al., 2011a; Figure SM1.1). The word representative signifies that each RCP provides only one of many possible pathways that would lead to the specific radiative forcing characteristics. The term pathway emphasises the fact that not only the long-term concentration levels, but also the trajectory taken over time to reach that outcome are of interest. Four RCPs were used for projections of the future climate in the 5th phase of the Coupled Model Intercomparison Project (CMIP5; Taylor et al., 2012). They are identified by their approximate anthropogenic radiative forcing (in W m-2, relative to 1750) by the year 2100: RCP2.6, RCP4.5, RCP6.0, and RCP8.5 (Figure SM1.1). RCP8.5 is a high greenhouse gas emission scenario without effective climate Subject to Copyedit 1-15 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere change mitigation policies, leading to continued and sustained growth in atmospheric greenhouse gas concentrations (Riahi et al., 2011). RCP2.6 represents a low greenhouse gas emission, high mitigation future that gives a two in three chance of limiting global atmospheric surface warming to below 2oC by the end of the century (van Vuuren et al., 2011b; Collins et al., 2013; Allen et al., 2018). Achieving the RCP2.6 pathway would require implementation of negative emissions technologies at a not-yet-proven scale to remove greenhouse gases from the air, in addition to other mitigation strategies such as energy from sustainable sources and existing nature-based strategies (Gasser et al., 2015; Sanderson et al., 2016; Royal Society, 2018; National Academies of Sciences, 2019). An even more stringent RCP1.9 pathway is considered most compatible with limiting global warming to below 1.5oC (called a 1.5°C-consistent pathway in SR1.5; O'Neill et al., 2016; IPCC, 2018), and will be assessed in AR6 using projections of Phase 6 of the Coupled Model Intercomparison Project (CMIP6). Global fossil CO₂ emissions rose more than 2% in 2018, and 1.6% in 2017, after a temporary slowdown in emissions from 2014 to 2016. Current emissions continue to grow in line with the RCP8.5 trajectory (Peters et al., 2012; Le Quéré et al., 2018). In SROCC, the CMIP5 simulations forced with RCPs are used extensively to assess future ocean and cryosphere changes. In particular, RCP2.6 and RCP8.5 are used to contrast the possible outcomes of low emission versus high emission futures, respectively (Table CB1.1). In some cases the SROCC assessments use literature that is based on the earlier Special Report on Emission Scenarios (SRES) (IPCC, 2000), and details of these and their approximate RCP equivalents are provided in Tables SM1.3 and SM1.4. Shared Socio-economic Pathways (SSPs) complement the RCPs with varying socio-economic challenges to adaptation and mitigation (e.g., population, economic growth, education, urbanisation and the rate of technological development; O’Neill et al., 2017). The SSPs describe five alternative socio-economic futures comprising: sustainable development (SSP1), middle-of-the-road development (SSP2), regional rivalry (SSP3), inequality (SSP4), and fossil-fuelled development (SSP5; Figure SM1.1; Kriegler et al., 2016; Riahi et al., 2017). The RCPs set plausible pathways for greenhouse gas concentrations and the climate changes that could occur, and the SSPs set the stage on which reductions in emissions will – or will not – be achieved within the context of the underlying socioeconomic characteristics and shared policy assumptions of that world. The combination of SSP-based socio-economic scenarios and RCP-based climate projections provides an integrative frame for climate impact and policy analysis. The SSPs will be included in the CMIP6 simulations to be assessed in AR6 (O'Neill et al., 2016). In SROCC, the SSPs are used only for contextualising estimates from the literature on varying future populations in regions exposed to ocean and cryosphere changes. Baselines and reference intervals. A baseline provides a reference period from which changes can be evaluated. In the context of anthropogenic climate change, the baseline should ideally approximate the ‘pre-industrial’ conditions before significant human influences on the climate began. AR5 and SR1.5 (Allen et al., 2018) use 1850–1900 as the ‘pre-industrial’ baseline for assessing historical and future climate change. Atmospheric greenhouse gas concentrations and global surface temperatures had already begun to rise in this interval from early industrialisation (Abram et al., 2016; Hawkins et al., 2017; Schurer et al., 2017). However, the scarcity of reliable climate observations represents a major challenge for quantifying earlier pre-industrial states (Hawkins et al., 2017). To maintain consistency across IPCC reports, the 1850–1900 pre-industrial baseline is used wherever possible in SROCC, recognising that this is a compromise between data coverage and representativeness of typical pre-industrial conditions. In SROCC, the 1986–2005 reference interval used in AR5 is referred to as the recent past, and a 2006–2015 reference is used for present day, consistent with SR1.5 (Allen et al., 2018). The 2006–2015 reference interval incorporates near-global upper ocean data coverage and reasonably comprehensive remote-sensing cryosphere data (Section 1.8.1), and aligns this report with a more current reference than the 1986–2005 reference adopted by AR5. This 10-year present day period is short relative to natural variability. However, at this decadal scale the bias in the ‘present-day’ interval due to natural variability is generally small compared to differences between ‘present-day’ conditions and the ‘pre-industrial’ baseline. There is also no indication of global average surface temperature in either 1986–2005 or 2006–2015 being substantially biased by short-term variability (Allen et al., 2018), consistent with the AR5 finding that each of the last Subject to Copyedit 1-16 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850 (IPCC, 2013). SROCC commonly provides future change assessments for two key intervals: A near term interval of 2031– 2050 is comparable to a single generation timescale from present day, and incorporates the interval when global warming is likely to reach 1.5oC if warming continues at the current rate (IPCC, 2018). An end-ofcentury interval of 2081–2100 represents the average climate conditions reached at the end of the standard CMIP5 future climate simulations, and is relevant to long-term infrastructure planning and climate-resilient development pathways (Cross-Chapter Box 2 in Chapter 1). In some cases where committed changes exist over multi-century timescales, such as the assessment of future sea-level rise (Section 4.3.2) or deep ocean oxygen changes (Section 5.2.4.2, Table 5.5), SROCC also considers model evidence for long-term changes beyond the end of the current century. Key indicators of future ocean and cryosphere change. Table CB1.1 compiles information on key indicators of climate change in the atmosphere and ocean. This information is given for different RCPs and for changes in the near term and end-of-century assessment intervals, relative to the recent past, noting that this does not capture changes that have already taken place since the pre-industrial baseline. AR5 assessed that global mean surface warming from the pre-industrial (1850-1900) to the recent past (1986-2005) reference period was 0.61oC (likely range of 0.55oC to 0.67oC). SR1.5 assessed that global mean surface temperature during the present day interval (2006-2015) was 0.87oC (likely range of 0.75oC to 0.99oC) higher than the average over the 1850-1900 pre-industrial period (very high confidence; IPCC, 2018). These key climate and ocean change indicators allow for some harmonisation of the risk assessments in the chapters of SROCC. Projections of future change across a wider range of ocean and cryosphere components is also provided in Figure 1.5. Ocean and cryosphere changes and risks by the end-of-century (2081-2100) are expected to be larger under high greenhouse gas emission scenarios, compared with low greenhouse gas emission scenarios (very high confidence) (Table CB1.1, Figure 1.5). Table CB1.1. Projected change in global mean surface air temperature and key ocean variables for the near-term (2031-2050) and end-of-century (2081-2100) relative to the recent past (1986-2005) reference period from CMIP5. See Table SM1.2 for the list of CMIP5 models and ensemble member used for calculating these projections. Small differences in the projections given here compared with AR5 (e.g., Table 12.2 in Collins et al., 2013) reflect differences in the number of models available now compared to at the time of the AR5 assessment (Table SM1.2). Near term: 2031-2050 End-of-century: 2081-2100 Scenario Mean 5-95% range Mean 5-95% range RCP2.6 0.9 0.5 to 1.4 1.0 0.3 to 1.7 RCP4.5 1.1 0.6 to 1.6 1.8 1.0 to 2.6 RCP6.0 1.0 0.5 to 1.5 2.3 1.3 to 3.2 RCP8.5 1.3 0.7 to 2.0 3.7 2.5 to 4.9 Global mean sea surface temperature (°C) b (section 5.2.5) RCP2.6 0.64 0.56 to 0.72 0.73 0.60 to 0.87 RCP8.5 0.95 0.86 to 1.03 2.58 2.34 to 2.82 Surface pH (units) b (section 5.2.2.3) RCP2.6 -0.072 -0.072 to -0.072 -0.065 -0.064 to -0.066 RCP8.5 -0.108 -0.107 to -0.109 -0.315 -0.314 to -0.317 Global mean surface air temperature (°C) a Subject to Copyedit 1-17 Total pages: 72 FINAL DRAFT Dissolved oxygen (100600 m) (% change) (section 5.2.2.4)b Chapter 1 IPCC SR Ocean and Cryosphere RCP2.6 -0.9 -0.6 to -1.2 -0.6 -0.3 to 0.9 RCP8.5 -1.4 -1.2 to -1.6 -3.9 -3.5 to -4.5 Notes: a Calculated following the same procedure as AR5 (Table 12.2 in Collins et al., 2013). The 5-95% model range of global mean surface air temperature across CMIP5 projections was assessed in AR5 as the likely range, after accounting for additional uncertainties or different levels of confidence in models. b The 5-95% model range for global mean sea surface temperature, surface pH and dissolved oxygen (100-600 m) as referred to in the SROCC assessment as the very likely range (Section 1.9.2, Figure 1.4). [END CROSS-CHAPTER BOX 1 HERE] 1.5 Risk and Impacts Related to Ocean and Cryosphere Change SROCC assesses the risks (i.e., potential for adverse consequences) and impacts (i.e., manifested risk) resulting from climate-related changes in the ocean and cryosphere. Knowledge on risk is essential for conceiving and implementing adequate responses. Cross-Chapter Box 2 in Chapter 1 introduces key concepts of risk, adaptation, resilience, and transformation, and explains why and how they matter for this report. In SROCC, the term ‘natural system’ describes the biological and physical components of the environment, independent of human involvement but potentially affected by human activities. ‘Natural systems’ may refer to portions of the total system without necessarily considering all its components (e.g., an ocean upwelling system). Throughout the assessment usage of ‘natural system’ does not imply a system unaltered by human activities. ‘Human systems’ include physiological, health, socio-cultural, belief, technological, economic, food, political, and legal systems, among others. Humans have depended upon the Earth’s ocean (WOA, 2016; IPBES, 2018b) and cryosphere (AMAP, 2011; Hovelsrud et al., 2011; Watt-Cloutier, 2018) for many millennia (Redman, 1999). Contemporary human populations still depend directly on elements of the ocean and cryosphere, and the ecosystem services they provide, but at a much larger scale and with greater environmental impact than in pre-industrial times (Inniss and Simcock, 2017). An ecosystem is a functional unit consisting of living organisms, their non-living environment, and the interactions within and between them. Ecosystems can be nested within other ecosystems and their scale can range from very small to the entire biosphere. Today, most ecosystems either contain humans as key organisms, or are influenced by the effects of human activities in their environment. In SROCC, a socialecological system describes the combined system and all of its subcomponents and refers specifically to the interaction of natural and human systems. The ocean and cryosphere are unique systems that have intrinsic value, including the ecosystems and biodiversity they support. Frameworks of Ecosystem Services and Nature’s Contributions to People are both used within SROCC to assess the impacts of changes in the ocean and cryosphere on humans directly, and through changes to the ecosystems that support human life and civilisations (Sections 2.3, 3.4.3.2, 4.3.3.5, 5.4, 6.4, 6.5, 6.8). The Millennium Ecosystem Assessment (MEA, 2005) established a conceptual Ecosystem Services framework between biodiversity, human well-being, and drivers of change. This framework highlights that natural systems provide vital life-support services to humans and the planet, including direct material services (e.g., food, timber), non-material services (e.g., cultural continuity, health), and many services that regulate environmental status (e.g., soil formation, water purification). This framework supports decision-making by quantifying benefits for valuation and trade-off analyses. The Ecosystem Services framework has been challenged as monetising the relationships of people with nature, and undervaluing small-scale livelihoods, cultural values, and other considerations that contribute little to global commerce (Díaz et al., 2018). More recent frameworks, such as Nature’s Contributions to People (Díaz et al., 2018), used in the Intergovernmental Platform on Biodiversity and Ecosystem Services assessments (IPBES), aim to better encompass the non-commercial ways that nature contributes to human quality of life. Subject to Copyedit 1-18 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere [START CROSS-CHAPTER BOX 2 HERE] Cross-Chapter Box 2: Key Concepts of Risk, Adaptation, Resilience and Transformation Authors: Matthias Garschagen (Germany), Carolina Adler (Switzerland/Australia), Susie Crate (USA), Hélène Jacot Des Combes (Fiji/France), Bruce Glavovic (New Zealand/South Africa), Sherilee Harper (Canada), Elisabeth Holland (Fiji/USA), Gary Kofinas (USA), Sean O'Donoghue (South Africa), Ben Orlove (USA), Zita Sebesvari (Hungary/Germany), Martin Sommerkorn (Norway/Germany) This box introduces key concepts used in the Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) in relation to risk, adaptation, resilience, and transformation. Building on an assessment of the current literature, it provides a conceptual framing for the report and for the assessments within its chapters. Full definitions of key terms are provided in SROCC Annex I: Glossary. Risk and adaptation SROCC considers risk from climate change-related effects on the ocean and cryosphere as the result of the interaction between: (1) environmental hazards triggered by climate change, (2) exposure of humans, infrastructure and ecosystems to those hazards, and (3) systems’ vulnerabilities. Risk refers to the potential for adverse consequences, and impacts refer to materialised effects of climate change. Next to assessing risk and impacts specifically resulting from climate change-related effects on the ocean, coast, and cryosphere, SROCC is also concerned with the options to reduce climate-related risk. Beyond mitigation, adaptation is a key avenue to reduce risk (Section 1.6). Adaptation can also include exploiting new opportunities; however, this box focuses on risk, and thus, the latter is not discussed in detail here. Adaptation efforts link into the causal fabric of risk by reducing existing and future vulnerability, exposure, and/or (where possible) hazards (Figure CB2.1). Addressing the different risk components (hazards, exposure and vulnerability) involves assessing and selecting options for policy and action. Such decision-making entails evaluation of the effectiveness, efficiency, efficacy, and acceptance of actions. Adaptation responses are more effective when they promote resilience to climate change, consider plausible futures and unexpected events, strengthen essential or desired characteristics as well as values of the responding system, and/or make adjustments to avoid unsustainable pathways (high agreement, medium evidence; Section 2.3; Box 2.4; 4.4.4; 4.4.5). Subject to Copyedit 1-19 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Figure CB2.1: There are options for risk reduction through adaptation. Adaptation can reduce risk by addressing one or more of the three risk factors: vulnerability, exposure, and/or hazard. The reduction of vulnerability, exposure, and/or hazard potential can be achieved through different policy and action choices over time until limits to adaptation might be reached. The figure builds on the conceptual framework of risk used in AR5 (Oppenheimer et al., 2014). Adaptation requires adaptive capacity, which for human systems includes assets (financial, physical, and/or ecological), capital (social and institutional), knowledge and technical know-how (Klein et al., 2014). The extent of adaptive capacity determines adaptation potential, but does not necessarily translate into effective adaptation if awareness of the need to act, the willingness to act, and/or the cooperation needed to act is lacking (high confidence; Sections 2.3; Box 2.4; 4.3.2.6.3; 5.5.2.4). There are limits to adaptation, which include, for example, physical, ecological, technological, economic, political, institutional, psychological, and/or socio-cultural aspects (medium evidence, high agreement) (Dow et al., 2013; Barnett et al., 2014; Klein et al., 2014). For example, the ability to adapt to sea level rise depends, in part, on the elevation of the low-lying islands and coasts in question, but also on the capacity to successfully negotiate protection or relocation measures socially and politically (Cross-Chapter Box 9, also see Section 6.4.3 for a wider overview). Limits to adaptation are sometimes considered as something different from barriers to adaptation. Barriers can in principle be overcome if adaptive capacity is available (e.g., where funding is made available), even though overcoming barriers is often hard in reality, particularly for resource-poor communities and countries (high confidence; Section 4.4.3). Limits to adaptation are reached when adaptation no longer allows an actor or ecosystem to secure valued objectives or key functions from intolerable risks (Section 4.4.2; Dow et al., 2013). Defining tolerable risks and key system functions is, therefore, of central importance for the assessment of limits to adaptation. Residual risks (i.e., the risk that endures following adaptation and risk reduction efforts) remain even where adaptation is possible (very high confidence; Chapters 2-6; Section 6.3.2; Table 6.2). Residual risks have bearing on the emerging debate about loss and damage (Huq et al., 2013; Warner and van der Geest, 2013; Boyd et al., 2017; Djalante et al., 2018; Mechler et al., 2018; Roy et al., 2018). This report addresses loss and damage in relation to slow onset processes, including ocean changes (Section 5.4.2.3), sea level rise (Section 4.3), and glacier retreat (Section 2.3.6), and polar cryosphere changes (Section 3.4.3.3.4), as well as rapid onset hazards such as tropical cyclones (Chapter 6). The assessment encompasses non-economic losses, including the impacts on intrinsic and spiritual attributes with which high mountain societies value their landscapes (Section 2.3.5); the interconnected relationship with, and reliance upon, the land, water, and ice for culture, livelihoods, and wellbeing in the Arctic (Section 3.4.3.3); and cultural heritage and displacement addressed in the integrative Cross-Chapter Box on low-lying islands and coasts (Cross-Chapter Box 9; Burkett, 2016; Markham et al., 2016; Tschakert et al., 2017; Huggel et al., 2018). Building resilience Addressing climate change-related risk, impacts (including extreme events and shocks), and trade-offs together with shaping the trajectories of social and ecological systems is facilitated by considering resilience (Biggs et al., 2012; Quinlan et al., 2016). In SROCC, resilience is understood as the capacity of interconnected social, economic, and ecological systems to cope with disturbances by reorganising in ways that maintain their essential function, structure, and identity (Walker et al., 2004). Resilience may be considered as a positive attribute of a system and an aspirational goal when it contributes to the capacity for adaptation and learning without changing the structure, function, and identity of the system (Walker et al., 2004; Steiner, 2015). Alternately, resilience may be used descriptively as a system property that is neither good nor bad (Walker et al., 2004; Chapin et al., 2009; Weichselgartner and Kelman, 2014). For example, a system can be highly resilient in keeping its unfavoured attributes, such as poverty or institutional rigidity (Carpenter and Brock, 2008). Critics of the resilience concept warn that the application of resilience to social systems is problematic when the responsibility for resilience building is shifted onto the shoulders of vulnerable and resource-poor populations (e.g., Chandler, 2013; Reid, 2013; Rigg and Oven, 2015; Tierney, 2015; Olsson et al., 2017). Applying the concept of resilience in mitigation and adaptation planning builds the capacity of a socialecological system to navigate anticipated changes and unexpected events (Biggs et al., 2012; Varma et al., 2014; Sud et al., 2015). Resilience also emphasises social-ecological system dynamics, including the Subject to Copyedit 1-20 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere possibility of crossing critical thresholds and experiencing a regime shift (i.e., state change). Seven general strategies for building social-ecological resilience have been identified (Figure CB2.2; Ostrom, 2010; Biggs et al., 2012; Quinlan et al., 2016). The concept of resilience also allows analysts, accessors of risk, and decision makers to recognise how climate-change related risks often cannot be fully avoided or alleviated despite adaptation. For SROCC, this is especially relevant along low-lying coasts, in high mountain areas, and in the polar regions (medium evidence, high agreement; Sections 2.3; 2.4; 3.5, 6.8, 6.9). Figure CB2.2: General strategies for enhancing social-ecological resilience to support climate-resilient pathways have been identified. The seven strategies are adapted from synthesis papers by Biggs et al. (2012) and Quinlan et al. (2016), the illustration of the CRDP builds on Figure SPM9 in AR5 (IPCC, 2014). Many efforts are underway to apply resilience thinking in assessments, management practices, policymaking, and the day-to-day practices of affected sectors and local communities. For example, leaders of the Pacific small island developing states use the Framework for Resilient Development in the Pacific, which integrates climate change and disaster risk management (Pacific Community, 2016; Cross-Chapter Box 9). In the Philippines, a new framework has been developed to conduct full inventories of actual and projected loss and damage due to climate change and associated disasters such as from cyclones. Creating such an inventory is difficult due to the disconnect between tools for climate change assessment and those for post disaster assessment (Florano, 2018). In Arctic Alaska, evaluative frameworks are being applied to determine needs, responsibilities, and alternative actions associated with coastal village relocations (Bronen, 2015; Cross-Chapter Box 9). In all these initiatives, resilience is a key consideration for enabling climate-resilient development pathways. Climate-resilient development pathways Climate-resilient development pathways (CRDPs) are a relatively new concept to describe climate change mitigation and adaptation trajectories that strengthen sustainable development and efforts to eradicate poverty and reduce inequalities while promoting fair and cross-scalar adaptation to, and resilience in, a changing climate (Kainuma et al., 2018; Roy et al., 2018). CRDPs are increasingly being explored as an approach for combining scientific assessments, stakeholder participation, and forward-looking development planning, acknowledging that pursuing CRDP is not only a technical challenge of risk management but also a social and political process (Roy et al., 2018). Adaptive decision-making over time is key to CRDPs (Haasnoot et al., 2013; Wise et al., 2014; Fazey et al., 2016; Ramm et al., 2017; Bloemen et al., 2018; Lawrence et al., 2018). CRDPs accommodate both the interacting cultural, social, and ecosystem factors that Subject to Copyedit 1-21 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere influence multi-stakeholder decision-making processes, and the overall sustainability of adaptation measures. Adequate climate change mitigation and adaptation allows for opportunities for sustainable development pathways and the options for resilience-building. CRDPs involve series of mitigation and adaptation choices over time, balancing short-term and long-term goals and accommodating newly available knowledge (Denton et al., 2014). The CRDPs approach has been successfully used, for example, in urban, remote, and disadvantaged communities, and can showcase the potential to counter maladaptive choices (e.g., Barnett et al., 2014; Butler et al., 2014; Maru et al., 2014). CRDPs aim to establish narratives of hope and opportunity that can extend beyond risk reduction and coping (Amundsen et al., 2018). Although climate change impacts on the ocean and cryosphere elicit many emotions—including fear, anger, despair, and apathy (Cunsolo Willox et al., 2013; Cunsolo and Landman, 2017; Cunsolo and Ellis, 2018)—narratives of hope are critical in provoking motivation, creative thinking, and behavioural changes in response to climate change (Myers et al., 2012; Smith and Leiserowitz, 2014; Feldman and Hart, 2016; Feldman and Hart, 2018; Prescott and Logan, 2018; Section 1.8.3). Much of the adaptation and resilience literature published since AR5 highlights the need for transformations that enable effective climate change mitigation (most notably, to decarbonise the economy) (Riahi et al., 2017), and support adaptation (e.g., Pelling et al., 2015; Few et al., 2017). Transformation becomes particularly relevant when existing mitigation and adaptation practices cannot reduce risks and impacts to an acceptable level. Transformative adaptation, therefore, involves fundamental modifications of policies, policy-making processes, institutions, human behaviour, and cultural values (Pelling et al., 2015; Solecki et al., 2017). Successful transformation requires attention to conditions that allow for such changes, including timing (e.g., windows of opportunity), social readiness (e.g., some level of willingness), and resources to act (e.g., trust, human skill, and financial resources; Kofinas et al., 2013; Moore et al., 2014). Examples related to SROCC include shifting from a paradigm of protection reliant on seawalls, to living with saltwater as a response to coastal flooding in rural areas (Renaud et al., 2015), or to involving fundamental risk management changes in coastal megacities, including retreat (Solecki et al., 2017). Transformation in changing ocean and cryosphere contexts can be fostered by transdisciplinary collaboration between actors in science, government, the private sector, civil society, and affected communities (Padmanabhan, 2017; CrossChapter Box 3 in Chapter 1; Cross-Chapter Box 4 in Chapter 1). [END CROSS-CHAPTER BOX 2 HERE] 1.5.1 Hazards and Opportunities for Natural Systems, Ecosystems, and Human Systems Hazards faced by marine and coastal organisms, and the ecosystem services they provide, are generally dependent on future greenhouse gas emission pathways, with moderate likelihood under a low emission future, but high to very high likelihood under higher emission scenarios (very high confidence) (Mora et al., 2013; Gattuso et al., 2015). Hazards to marine ecosystems assessed in AR5 (IPCC, 2014) included degradation of coral reefs (high confidence), ocean deoxygenation (medium confidence), and ocean acidification (high confidence). Shifts in the ranges of plankton and fish were identified with high confidence regionally, but with uncertain trends globally. SROCC provides more evidence for global shifts in the distribution of marine organisms, and in how the phenology of animals is responding to ocean change (Sections 3.2.3, 5.2). The signature of climate change is now detected in almost all marine ecosystems. Similar trends of changing habitat due to climate change are reported for the cryosphere (Sections 2.2, 3.4.3.2). The risk of irreversible loss of many marine and coastal ecosystems increases with global warming, especially at 2°C or more (high confidence; IPCC, 2018). Risk also increases for habitat displacements, both poleward (Section 3.2.4) and to greater ocean depths (Section 5.2.4), or habitat reductions, such as caused by glacier retreat (Section 2.2.3). Changes in the ocean and cryosphere bring hazards that affect the health, wellbeing, safety, and security of populations in coastal, mountain, and polar environments (Section 2.3.5, 3.4.3, 4.3.2). Some impacts are direct, such as sea level rise or coastal erosion that can displace coastal residents (4.3.2.3, 4.4.2.6, Box 4.1). Other effects are indirect; for example, rising ocean temperatures have led to increases in maximum wind speed and rainfall rates in tropical cyclones (Section 6.3), creating hazards with severe consequences for Subject to Copyedit 1-22 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere natural and human systems (Sections 4.3, 6.2, 6.3, 6.8). The multiple category 4 and 5 Atlantic hurricanes in 2017 caused the loss of over 3300 lives and more than 350 billion US$ in economic damages (Cross-Chapter Box 9; Andrade et al., 2018; Murakami et al., 2018; NOAA, 2018). In mountain regions, glacial lake outburst floods have caused severe impacts on lives, livelihoods, and infrastructure that often extend beyond the directly affected areas (Section 2.3.2 and 6.2.2). Some hazards related to ocean and cryosphere change involve abrupt and irreversible changes (Section 1.3), which generate sometimes unpredictable risks, and multiple hazards can coincide to greatly elevate the total risk (Section 6.8.2). For example, combinations of thawing permafrost, sea level rise, loss of sea ice, ocean surface waves, and extreme weather events (Thomson and Rogers, 2014; Ford et al., 2017) have damaged Arctic infrastructure (e.g., buildings, roads) (AMAP, 2015; AMAP, 2017); impacted reindeer husbandry livelihoods for Sami and other Arctic Indigenous peoples; and impeded access to hunting grounds, other communities, and travel routes fundamental to the livelihoods, food security, and wellbeing of Inuit and other Northern cultures (Section 3.4.3). In some Arctic regions, tipping points may have already been reached such that adaptive practices can no longer work (Section 3.5).` Climate change impacts on the ocean and cryosphere can also present opportunities, in at least the near- and medium-term. For example, in Nepal warming of high-mountain environments and accelerated melting of snow and ice have extended the growing season and crop yields in some regions (Section 2.3; Gaire et al., 2015; Merrey et al., 2018), while tourism and shipping has increased in the Arctic with loss of sea ice (Section 3.2.4). Moreover, rising ocean temperatures redistribute the global fish population, allowing new fishing opportunities while reducing some established fisheries (Bell et al., 2011; Fenichel et al., 2016; Section 5.4). To gain from new opportunities, while also avoiding or mitigating new or increasing hazards, it is necessary to be aware of trade-offs between risks and benefits to understand who is and is not benefiting. For example, opportunities can involve trade-offs with mitigation and/or SDGs (Section 3.5.2), and the balance of economic costs and benefits may differ substantially between the near-term and long-term future (Section 5.4.2.2). 1.5.2 Exposure of Natural Systems, Ecosystems, and Human Systems Exposure to hazards in cryosphere systems occur in the immediate vicinity of cryosphere components, and at regional to global scales where cryosphere changes link to other natural systems. For example, decreasing Arctic sea ice increases exposure for organisms that depend upon habitats provided by sea ice, but also has far-reaching impacts through the resulting direct albedo feedback and amplification of Arctic climate warming (e.g., Pistone et al., 2014) that then locally increases surface melting of the Greenland ice sheet (Liu et al., 2016; Stroeve et al., 2017). Additionally, ice loss from ice sheets contribute to the global-scale exposure of sea level rise, and more local-scale modifications and losses of coastal habitats and ecosystems (Sections 3.2.3 and 4.3.3.5). Interactions within and between natural systems also influence the spatial reach of risks associated with cryosphere change. Permafrost degradation, for example, interacts with ecosystems and climate on various spatial and temporal scales, and feedbacks from these interactions range from local impacts on topography, hydrology and biology, to global scale impacts via biogeochemical cycling (e.g., methane release) on climate (Sections 2.2, 2.3, 3.4; Kokelj et al., 2015; Grosse et al., 2016). Exposure to climate change risk exists for virtually all coastal organisms, habitats and ecosystems (Section 5.2), through processes such as inundation and salinisation (Section 4.3), ocean acidification and deoxygenation (Sections 3.2.3, 5.2.3), increasing marine heatwaves (Section 6.4.1.2), and increases in harmful algal blooms and invasive species (Glibert et al., 2014; Gobler et al., 2017; Townhill et al., 2017; Box 5.3). Aggregate impacts of multiple drivers are dramatically altering ecosystem structure and function in the coastal and open ocean (Boyd et al., 2015; Deutsch et al., 2015; Przeslawski et al., 2015), such as coral reefs under increasing pressure from both rising ocean temperature and acidification (Section 5.3.4). Increasing exposure to climate change hazards in open ocean natural systems includes ocean acidification (O'Neill et al., 2017; Section 5.2.3), changes in ocean ventilation, deoxygenation (Shepherd et al., 2017; Breitburg et al., 2018; Section 5.2.2.4), increased cyclone and flood risk (Section 6.3.3), and an increase in extreme El Niño and La Niña events (Section. 6.5.1). Heat content is rapidly increasing within the ocean (Section 5.2.2), and marine heat waves are becoming more frequent across the world ocean (Section 6.4.1). People who live close to the ocean and/or cryosphere, or depend directly on their resources for livelihoods, are particularly exposed to climate change impacts and hazards (very high confidence) (Barange et al., 2014; Subject to Copyedit 1-23 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Romero-Lankao et al., 2014; AMAP, 2015). These exposures can result in infrastructure damage and failure (Sections 2.3.1.3, 3.4.3, 3.5., 4.3.2); loss of habitability (Sections 2.3.7, 3.4.3, 3.5, 4.3.3); changes in air quality (Section 6.5.2); proliferation of disease vectors (Sections 3.4.3.2.2, 5.4.2.1.1); increased morbidity and mortality due to injury, infectious disease, heat stress, and mental health and wellness challenges (Section 3.4.3.3); compromised food and water security (Sections 2.3.1, 3.4.3.3, 4.3.3.6, 5.4.2.1, 6.8.4); degradation of ecosystem services (Sections 2.3.1.2, 2.3.3.4, 4.3.3, 5.4.1, 6.4.2.3); economic and noneconomic impacts due to reduced production and social network system disruption (Section 2.3.7); conflict (Sections 2.3.1.14, 3.5); and widespread human migration (Sections 2.3.7, 4.4.3.5; Oppenheimer et al., 2014; van Ruijven et al., 2014; AMAP, 2015; Cunsolo and Ellis, 2018). This report documents how people residing in coastal and cryosphere regions are already exposed to climate change hazards, and which of these hazards are projected to increase in the future. For example, mountain communities have been exposed to increased rockfall, rock avalanches, and landslides due to permafrost degradation and glacier shrinkage, and to changes in snow avalanche type and seasonal timing (Section 2.3.1). Cryosphere changes that can impact water availability in mountain regions and for downstream populations (Sections 2.3.1, 2.3.4, 2.3.5) have implications for drinking water, irrigation, livestock grazing, hydropower production, and tourism (Section 2.3). Some declining mountain glaciers hold sacred and symbolic meanings for local communities who will experience spiritual losses (Section 2.3.4, 2.3.5, and 2.3.6). Exposures to extreme warming, and continued sea-ice and permafrost loss in the Arctic, challenge Indigenous communities with close interdependent relationships of economy, life-styles, cultural identity, self-sufficiency, Indigenous knowledge, health and wellbeing with the Arctic cryosphere (Section 3.4.3, 3.5). The population living in low elevation coastal zones (land less than 10 m above sea level) is projected to increase to more than one billion by 2050 (Section 4.3.2.2). These people and communities are particularly exposed to future sea level rise, rising ocean temperature (including marine heat waves; Section 6.4), enhanced coastal erosion, increasing wind, wave height, storm intensity, and ocean acidification (Section 4.3.4). These exposures bring associated risks for livelihoods linked to fisheries, tourism and trade, as well as loss of life, damaged assets, and disruption of basic services including safe water supplies, sanitation, energy, and transportation networks (Chapters 4, 5, and 6; Cross-Chapter Box 9). 1.5.3 Vulnerabilities in Natural Systems, Ecosystems, and Human Systems Direct and indirect risks to natural systems are influenced by vulnerability to climate change as well as deterioration of ecosystem services. For example, about half of species assessed on the northeast United States continental shelf exhibited high to very high climate vulnerability due to temperature preferences and changes in habitat space (Hare et al., 2016), with corresponding northward range shifts for many species (Kleisner et al., 2017) and increased vulnerability for organisms or ecosystems unable to migrate or evolve at the rate required to adapt to ocean and cryosphere changes (Miller et al., 2018). Non-climatic pressures also magnify the vulnerability of ocean and cryosphere ecosystems to climate-related changes, such as overfishing, coastal development, and pollution, including plastic pollution (Halpern et al., 2008; Halpern et al., 2015; IPBES, 2018a; IPBES, 2018b; IPBES, 2018c; IPBES, 2018d). Conventional (fossil fuel-based) plastics produced in 2015 accounted for 3.8% of global CO2 emissions and could reach up to 15% by 2050 (Zheng and Suh, 2019). The vulnerability of mountain, Arctic, and coastal communities is affected by social, political, historical, cultural, economic, institutional, environmental, geographical, and/or demographic factors such as gender, age, race, class, caste, Indigeneity, and disability (Thomas et al., 2019; Sections 2.3.6 and 3.5; Cross-Chapter Box 9). Disparities and inequities in such factors may result in social exclusion, inequalities, and nonclimatic challenges to health and wellbeing, economic development and basic human rights (Adger et al., 2014; Olsson et al., 2014; Smith et al., 2014). Those less advantaged often also have reduced access to and control over the social, financial, technological, and environmental resources that are required for adaptation and transformation (Oppenheimer et al., 2014; AMAP, 2015), thus limiting options for coping and adapting to change (Hijioka et al., 2014). However, even populations with greater wealth and privilege can be vulnerable to some climate change risks (Cardona et al., 2012; Smith et al., 2014), especially if sources of wealth and wellbeing, depend upon established infrastructure that is poorly suited to ocean or cryosphere change. Subject to Copyedit 1-24 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Institutions and governance can shape vulnerability and adaptive capacity, and it can be challenging for weak governance structures to respond effectively to extreme or persistent climate change hazards (Sections 6.4 and 6.9; Cross-Chapter Box 3 in Chapter 1; Berrang-Ford et al., 2014; Hijioka et al., 2014). Furthermore, populations can be negatively impacted by inappropriate climate change mitigation and/or adaptation policies, particularly ones that further marginalise their knowledge, culture, values, and livelihoods (Field et al., 2014; Cross-Chapter Box 4 in Chapter 1). Vulnerability is not static in place and time, nor homogeneously experienced. The vulnerabilities of individuals, groups, and populations to climate change is dynamic and diverse, and reflects changing societal and environmental conditions (Thomas et al., 2019). SROCC examines vulnerability following the conceptual definition presented in Cross-Chapter Box 2 in Chapter 1, and vulnerability in human systems is treated in relative, rather than absolute terms. 1.6 Addressing the Causes and Consequences of Climate Change for the Ocean and Cryosphere Effective and ambitious mitigation of climate change would be required to meet the temperature goal of the Paris Agreement (UNFCCC, 2015; IPCC, 2018). Similarly, effective and ambitious adaptation to climate change impacts on the ocean and cryosphere is necessary to enable climate-resilient development pathways that minimise residual risk, and loss and damage (very high confidence; Cross-Chapter Box 2 in Chapter 1; IPCC, 2018). Mitigation refers to human actions to limit climate change by reducing the emissions and enhancing the sinks of greenhouse gases. Adaptation refers to processes of adjustment by natural or human systems to actual or expected climate and its effects, intended to moderate harm or exploit beneficial opportunities. The presidency of the 23rd Conference of the Parties (COP23) of United Nations Framework Convention on Climate Change (UNFCCC) introduced the oceans pathway into the climate solution space, acknowledging both the importance of the ocean in the climate system and that ocean commitments for adaptation and mitigation are available through Nationally Determined Contributions (NDC) under the UNFCCC (Gallo et al., 2017). 1.6.1 Mitigation and Adaptation Options in the Ocean and Cryosphere Mitigation and adaptation pathways to avoid dangerous anthropogenic interference with the climate system (United Nations, 1992) are considered in SR1.5 (IPCC, 2018). SROCC assesses several ocean and cryosphere-specific measures for mitigation and adaptation including options for to address the causes of climate change, support biological and ecological adaptation, and enhance societal adaptation (Figure 1.2). Other measures have been proposed, including solar radiation management and several other forms of carbon dioxide removal, but these are not addressed in SROCC as they are covered in other products of the IPCC Sixth Assessment Cycle (SR1.5 and AR6 Working Group III) and are outside the scope of SROCC. SROCC does assess indirect mitigation measures that involve the ocean and the cryosphere (Figure 1.2) by supporting biological and ecological adaptation, such as through reducing nutrient and organic carbon pollution (which moderates ocean acidification in eutrophied areas) and conservation (which preserves biodiversity and habitats) in coastal regions (Billé et al., 2013). A literature-based expert assessment shows that ocean-related mitigation measures have trade-offs, with the greatest benefits derived by combining global and local measures (high confidence; Gattuso et al., 2018). Local measures, such as pollution reduction and conservation, provide significant co-benefits and few adverse side-effects (high confidence; Sections 5.5.1, 5.5.2). They can be relatively rapidly implemented, but are generally less effective in addressing the global problem (high confidence; Sections 5.5.1, 5.5.2). Likewise, local efforts to decrease air pollution near mountain glaciers and other cryosphere components, for example reducing black carbon emissions, can bring regional-scale benefits for health and in reducing snow and ice melt (Shindell et al., 2012; Box 2.2). Well-chosen human interventions can enhance the adaptive capacity of natural systems to climate change. Such interventions through manipulating an ecosystem’s structural or functional properties (e.g., restoration of mangroves) may minimise climate change pressures, enhance natural resilience and/or re-direct ecosystem responses to reduce cascading risks on societies. In human systems, adaptation can involve both infrastructure (e.g., enhanced sea defences) and community-based action (e.g., changes in policies and Subject to Copyedit 1-25 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere practices). Adaptation options to ongoing climate change are most effective when considered together with mitigation strategies because there are limits to effective adaptation, mitigation actions can make adaptation more difficult, and some adaptation measures may increase greenhouse gas emissions. Adaptation and mitigation decisions are connected with economic concerns. In SROCC, two main economic approaches are used. The first comprises the Total Economic Value method and the valuation of ecosystem services. SROCC considers the paradigm of sustainable development, and the linkages between climate impacts on ecosystem services (Section 5.4.1) and the consequences on sustainable development goals including food security or poverty eradication (Section 5.4.2). The second economic approach used are formal decision analysis methods, which help to identify options (also called alternatives) that perform best or well with regards to given objectives. These methods include cost-benefit analysis, multi-criteria analysis and robust decision-making and are specifically relevant for appraising long-term investment decisions in the context of coastal adaptation (Section 4.4.4.6). Figure 1.2. Overview of the main ocean-cryosphere mitigation and adaptation measures to observed and expected changes in the context of this report. A longer description of these measures are given in SM1.3. Solar radiation management techniques are omitted because they are covered in other AR6 products. Governance and enabling conditions are implicitly embedded in all mitigation and adaptation measures. Some governance-based measures (e.g., institutional arrangements) are not included in this figure but are covered in Cross-Chapter Box 3 in Chapter 1 and in Chapters 2 to 6. GHG: greenhouse gases. Modified from Gattuso et al. (2018). 1.6.2 Adaptation in Natural Systems, Ecosystems, and Human Systems In AR5, a range of changes in ocean and cryosphere natural systems were linked with medium to high confidence to pressures associated with climate change (Cramer et al., 2014). Climate change impacts on natural ecosystems are variable in space and time. The multiplicity of pressures these natural systems experience impedes attribution of population or ecosystem responses to a specific ocean and/or cryosphere change. Moreover, the interconnectivity of populations within ecosystems means that a single ‘adaptive response’ of a population, or the aggregate response of an ecosystem (the adaptive responses of the interconnected populations), is influenced not just by direct pressures of climate change, but occurs in concert with the adaptive responses of other species in the ecosystem, further complicating efforts to disentangle specific patterns of adaptation. Notwithstanding the network of pressures and adaptations, much effort has gone into resolving the mechanisms, interactions, and feedbacks of natural systems associated with the ocean and cryosphere. Chapters 4, 5, and 6 as well as Cross-Chapter Box 9 assess new knowledge on the adaptive responses of wetlands, coral reefs, other coastal habitats, and the populations of marine organisms encountering ocean- Subject to Copyedit 1-26 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere based risks, including. Likewise, Chapters 2 and 3 describe emerging knowledge on how ecosystems in high-mountain and polar areas are adapting to cryosphere decline. AR5 and SR1.5 have highlighted the importance of evolutionary adaptation as a component of how populations adapt to climate change pressures (e.g., Pörtner et al., 2014; Hoegh-Guldberg et al., 2018). Acclimatisation (variation in morphology, physiology or behaviour) can result from changes in gene expression but does not involve change in the underlying DNA sequence. Responses related to acclimatisation can occur both within single generations and over several generations. In contrast, evolution requires changes in the genetic composition of a population over multiple generations; for example, by differential survival or fecundity of different genotypes (Sunday et al., 2014). Adaptive evolution is the subset of evolution attributable to natural selection, and natural selection may lead to populations becoming more fit (Sunday et al., 2014) or extend the range of environments where populations persist (van Oppen et al., 2015). The efficacy of natural selection is affected by population size (Charlesworth, 2009), standing genetic variation, the ability of a population to generate novel genetic variation, migration rates, and the frequency of genetic recombination (Rice, 2002). Many studies have shown evolution of traits within and across life-stages of populations (Pespeni et al., 2013; Hinners et al., 2017), but there are fewer studies on how evolutionary change can impact ecosystem or community function, and whether trait evolution is stable (Schaum and Collins, 2014). Although acclimatisation and evolutionary adaptation are separate processes, they influence each other, and both adaptive and maladaptive variation of traits can facilitate evolution (Schaum and Collins, 2014; Ghalambor et al., 2015). Natural evolutionary adaptation may be challenged by the speed and magnitude of current ocean and cryosphere changes, but emerging studies investigate how human actions may assist evolutionary adaptation and thereby possibly enhance the resilience of natural systems to climate change pressures (e.g., Box 5.4 in Section 5.5.2). Through acclimatisation and evolutionary adaptation to the pressures from climate change (and all other persistent pressures), populations, species and ecosystems present a constantly changing context for the adaptation of human systems to climate change. There are several human adaptation options for climate change impacts on the ocean and cryosphere. Adaptive responses include nature- and ecosystem-based approaches (Renaud et al., 2016; Serpetti et al., 2017). Additionally, more social-based approaches for human adaptation range from community-based and infrastructure-based approaches to managed retreat, along with other forms of internal migration (Black et al., 2011; Hino et al., 2017). Building on AR5 (Wong et al., 2014), Chapter 4 describes four main modes of adaptation to mean and extreme sea level rise: protect, advance, accommodate, and retreat. This report demonstrates that all modes of adaptation include mixes of institutional, individual, socio-cultural, engineering, behavioural, and/or ecosystem-based measures (e.g., Section 4.4.2). The effectiveness and performance of different adaptation options across spatial and social scales is influenced by their social acceptance, political feasibility, cost-efficiency, co-benefits, and trade-offs (Jones et al., 2012; Adger et al., 2013; Eriksen et al., 2015). Scientific evaluation of past successes and future options, including understanding barriers, limits, risks, and opportunities, are complex and inadequately researched (Magnan and Ribera, 2016). In the end, adaptation priorities will depend on multiple parameters including the extent and rate of climate change, the risk attitudes and social preferences of individuals and institutions (and the returns they may gain) (Adger et al., 2009; Brügger et al., 2015; Evans et al., 2016; Neef et al., 2018), and access to finances, technology, capacity, and other resources (Berrang-Ford et al., 2014; Eisenack et al., 2014). Since AR5, transformational adaptation (i.e., the need for fundamental changes in private and public institutions and flexible decision-making processes to face climate change consequences) has been increasingly studied (Cross-Chapter Box 2 in Chapter 1). The recent literature documents how societies, institutions, and/or individuals increasingly assume a readiness to engage in transformative change, via their acceptance and promotion of fundamental alterations in natural or human systems (Klinsky et al., 2016). People living in and near coastal, mountain, and polar environments often pioneer these types of transformations, since they are at the forefront of ocean and cryosphere change (e.g., Solecki et al., 2017). Community-led and Indigenous-led adaptation research continues to burgeon (Ayers and Forsyth, 2009; David-Chavez and Gavin, 2018), especially in many mountain (Section 2.3.2.3), Arctic (Section 3.5), and coastal (Section 4.4.4.4, 4.4.5.4, Cross-Chapter Box 9) areas, and demonstrate potential for enabling transformational adaptation (Dodman and Mitlin, 2013; Chung Tiam Fook, 2017). Similarly, the concepts of Subject to Copyedit 1-27 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere scenario planning and 'adaptation pathway' design have expanded since AR5, especially in the context of development planning for coastal and delta regions (Section 4.4, Cross-Chapter Box 9; Wise et al., 2014; Maier et al., 2016; Bloemen et al., 2018; Flynn et al., 2018; Frame et al., 2018; Lawrence et al., 2018). 1.7 Governance and Institutions SROCC conceptualises governance as deciding, managing, implementing and monitoring policies in the context of ocean and cryosphere change. Institutions are defined as formal and informal social rules that shape human behaviour (Roggero et al., 2017). Governance guides how different actors negotiate, mediate their interests, and share their rights and responsibilities (Forino et al., 2015; See SROCC Annex I: Glossary and Cross-Chapter Box 3 in Chapter 1 for definition). Governance and institutions interface with climate and social-ecological change process across local, regional to global scales (Fischer et al., 2015; Pahl-Wostl, 2019). SROCC explores how the interlinked social-ecological systems affect challenge current governance systems in the context of ocean and cryosphere change. These challenges include three aspects. First, the scale of changes to ocean and cryosphere properties driven by global warming, and in the ecosystems, they support and services they provide, are poorly matched to existing scales of governance (Sections 2.2.2.1; 2.3.1.3; 3.2.1; 3.5.3). Second, the nature of changes in ecosystem services resulting from changes in ocean and cryosphere properties, including services provided to humans living far from the mountains and coasts, are poorly matched to existing institutions and processes (Section 4.4.4). Third, many possible governance responses to these challenges could be of limited or diminished effectiveness unless they are coordinated on scales beyond that of currently available governance options (Section 6.9.2; Box 5.5) Hydrological processes in the high mountain cryosphere connect through upstream and downstream areas of river basins (Molden et al., 2016; Chen et al., 2018), including floodplains and deltaic regions (Kilroy, 2015; Cross-Chapter Box 3 in Chapter 1). These cross-boundary linkages challenge local-scale governance and institutions that determine how the river-based ecosystem services that sustain food, water, and energy are used and distributed (Rasul, 2014; Warner, 2016; Lele et al., 2018; Pahl-Wostl et al., 2018). Small Island States face rising seas that threaten habitability of their homeland and the possibility of losing their nationstate, cultural identity and voices in international governance (Gerrard and Wannier, 2013; Philip, 2018; Section 1.4, Cross-Chapter Box 9), highlighting the need for transboundary components to governance. These governance challenges cannot be met without working across multiple organisations and institutions, bringing varying capacities, frameworks and spatial extents (Cross-Chapter Box 3 in Chapter 1). Progress in governance for ocean and cryosphere change will require filling gaps in legal frameworks (Amsler, 2016), aligning spatial mismatches (Eriksen et al., 2015; Young, 2016; Cosens et al., 2018), improving the ability for nations to cooperate effectively (Downie and Williams, 2018; Hall and Persson, 2018), and integrating across divided policy domains, most notably of climate change adaptation and disaster risk reduction (e.g. where slow sea level change also alters the implications for civil defense planning and the management of extreme events; Mysiak et al., 2018). Harmonising local, regional and global governance structures would provide an overarching policy framework for action and allocation of necessary resources for adaptation. Coordinating the top-down and bottom-up governance processes (Bisaro and Hinkel, 2016; Sabel and Victor, 2017; Homsy et al., 2019) to increase effectiveness of responses, mobilise and equitably distribute adequate resources, and access private and public sector capabilities requires a polycentric approach to governance (Ostrom, 2010; Jordan et al., 2015). Polycentric governance connotes a complex form of governance with multiple centers of decisionmaking working with some degree of autonomy (Carlisle and Gruby, 2017; Baldwin et al., 2018; Mewhirter et al., 2018; Hamilton and Lubell, 2019). [START CROSS-CHAPTER BOX 3 HERE] Cross-Chapter Box 3: Governance of the Ocean, Coasts and the Cryosphere under Climate Change Subject to Copyedit 1-28 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Authors: Anjal Prakash (Nepal/India), Sandra Cassotta (Denmark), Bruce Glavovic (New Zealand/South Africa), Jochen Hinkel (Germany), Elisabeth Holland (Fiji/USA), Md Saiful Karim (Australia/Bangladesh), Ben Orlove (USA), Beate Ratter (Germany), Jake Rice (Canada), Evelia Rivera-Arriaga (Mexico), Catherine Sutherland (South Africa) This Cross-Chapter Box outlines governance and associated institutional challenges and emerging solutions relevant to the ocean, coasts and cryosphere in a changing climate. It illustrates these through three cases: [1] multi-level interactions in Ocean and Arctic governance; [2] mountain governance; and [3] coastal risk governance. Governance refers to how political, social, economic and environmental systems and their interactions are governed or ‘steered’ by establishing and modifying institutional and organisational arrangements, which regulate social processes, mitigate conflicts and realise mutual gains (North, 1990; Pierre and Peters, 2000; Paavola, 2007). Institutions are formal and informal rules and norms, constructed and held in common by social actors, that guide, constrain and shape human interactions (North, 1990; Ostrom, 2005). Formal institutions include constitutions, laws, policies and contracts, while informal institutions include customs, social norms and taboos. Both administrative or state government structures, and indigenous or traditional governance structures govern the ocean, coasts and cryosphere. Understanding governance in a changing climate SROCC, together with SR1.5 (IPCC, 2018), highlights the critical role of governance in implementing effective climate adaptation. Chapter 2 explores local community institutions offering autonomous adaptation in the Alps, Andes, Himalayas and other mountain regions (Section 2.4), focusing on the need for transboundary cooperation to support water governance and mitigate conflict. Chapter 3 explores how polar governance system facilitate building resilient pathways, knowledge co-production, social learning, adaptation, and power-sharing with Indigenous Peoples at the regional level. This would help in increasing international cooperation in multi-level governance arenas to strengthen responses supporting adaptation in socio-ecological systems (Section 3.5.4). Chapter 4 illustrates how sea level rise governance attempts to address conflicting interests in coastal development, risk management and adaptation with a diversity of governance contexts and degrees of community participation, with a focus on equity concerns and inevitable trade-offs (Section 4.4). Chapter 5 includes a review of existing international legal regimes for addressing ocean warming, acidification and deoxygenation impacts on socio-ecological systems and considers ways to facilitate appropriate responses to ocean change (Sections 5.4, 5.5). Chapter 6 explores the issues of credibility, trust, and reliability in government that arise from promoting ‘paying the costs of preparedness and prevention’ as an alternative to ‘bearing the costs of loss and damage’ (Section 6.9). Climate change challenges existing governance arrangements in a variety of ways. First, there are complex interconnections between climate change and other processes that influence the ocean, coasts and cryosphere, making it difficult to untangle climate governance from other governance efforts. Second, the timeframes of for societal decision-making and government terms are mismatched with the long-term commitment of climate change. Third, governance choices have to be made in the face of uncertainty about the rate and scale of change that will occur in the medium to long-term (Cross-Chapter Box 5 in Chapter 1). Lastly, climate change progressively alters the environment and hence requires continual innovation and adjustment of governance arrangements (Bisaro and Hinkel, 2016; Roggero et al., 2018). Novel transboundary interactions and conflicts are emerging as well as new multi-level governance structures for international and regional cooperation, strengthening shared decision-making among States and other actors (Case 1). The prospects of “disappearing states”, glacier retreat, and increasing water scarcity, are resulting in States redefining complex water-sharing agreements (Case 2). Coastal risk is escalating, which may require participatory governance responses and the co-production of knowledge at the local scale (Case 3; see also Cross-Chapter Box 9). Governance, exercised through legal, administrative and other social processes, is essential to prevent, mitigate and adapt to the challenges and risks posed by a changing climate. These governance processes determine roles in the exercising of power and hence decision-making (Graham et al., 2003). Governance may be an act of governments (e.g. passing laws, providing incentives or information such that citizens can respond more effectively to climate change); private sector actions (e.g., insurance); a co-operative effort among local actors governing themselves through customary law (e.g., by establishing entitlements or norms regulating the common use of scarce resources); a collaborative multi-level effort involving multiple actors (state, private and civil society; e.g., UNFCCC); or a multi-national effort (e.g., Antarctic Treaty; see Figure Subject to Copyedit 1-29 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere CB3.2). The complexities of governance arrangements in the ocean, coasts and cryosphere (Figure CB3.1), and the interactions and emergence of relationships between different governance actors in multiple configurations across various spatial scales (Figure CB3.2) are illustrated below. Figure CB3.1: Spatial distribution of multi-faceted governance arrangements for the ocean, coasts and cryosphere (Panel A) sovereignty, sovereign rights, jurisdictions and freedoms defined for different ocean zones and sea by UNCLOS (Panel B). Figure CB3.1 is designed to be illustrative and is not comprehensive of all governance arrangements for the ocean, coasts and cryosphere Subject to Copyedit 1-30 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Figure CB3.2: Interactions and emergence of network governance arrangements for the ocean, coasts and cryosphere across different scales. Adapted from Sommerkorn and Nilsson (2015). Case Study 1 — Multi-level Interactions and Synergies in Governance. The UN Convention on the Law of the Sea and the changing Arctic: Climate-change induced sea-level rise (Section 4.2), could shift the boundaries and territory of some coastal states, changing the areas where their coastal rights are applied under the United Nations Convention on the Law of the Sea (UNCLOS). In extreme cases, inundation from sea level rise might lead to loss of territory and sovereignty, the disappearance of islands and the loss of international maritime jurisdiction subject to maritime claim. These challenges have limited opportunities for recourse in international law and it remains unclear what adequate responses from an international law perspective would be (Vidas et al., 2015; Andreone, 2017; Mayer and Crépeau, 2017; Chircop et al., 2018). While specific legal arrangements and instruments of environmental protection are in place at a regional, sub-regional and national level, they are insufficient to address the new challenges sea level rise brings. Institutional responses to the geopolitical transformation caused by climate change, such as through the Arctic Council (AC) and the ‘Law of the Sea’ are still evolving. Similar to many international agreements, UNCLOS ‘Law of the Sea’ provisions for enforcement, compliance, monitoring and dispute settlement mechanisms are not comprehensive, and commonly depend on further, detailed law-making by state parties, acting through competent international organizations (Vidas, 2000; Karim, 2015; De Lucia, 2017; Grip, 2017). Shifts from traditional state-based practices of international law to multi-level and informal governance structures that involve state and non-state actors (including Indigenous Peoples) may address these challenges (medium confidence; Cassotta, 2012; Shadian, 2014; Young, 2016; Andreone, 2017). The Arctic Council (AC), is a regionally focused governance structure blending new forms of formal and informal multi-level regional cooperation (Young, 2016). The soft law mechanisms employed draw upon best available practice and standards from multiple knowledge systems (Cassotta and Mazza, 2015; Pincus and Ali, 2015) in an attempt to respond to the ocean’s global, trans-regional and national climate challenges (Section 3.5.4.2). Reconfiguration and restructuring of the AC has been proposed in order to address emerging trans-regional and global problems (high confidence; Baker and Yeager, 2015; Pincus and Ali, 2015; Young, 2016). Within the existing scope, the AC has amplified the voice of Arctic people affected by the impacts of climate change and mobilized action (Koivurova, 2016). The influence of actors ‘beyond the state’ is emerging (Figure CB3.2). However, the state retains its importance in tackling the new challenges produced by climate change, as the role of international cooperation in UNCLOS and the Polar Regions demonstrates (Section 3.5.4.2). For example, Article 234 (“Ice-covered areas”) and Article 197 of the UNCLOS Convention in protecting the marine environment, states that “States shall cooperate on a global basis and, as appropriate, on a regional basis […] taking into account characteristic regional features”. Subject to Copyedit 1-31 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Case Study 2 — Mountain Governance: Water management in Gilgit-Baltistan, Pakistan. Gilgit-Baltistan is an arid territory in a mountainous region of northern Pakistan. Meltwater-fed streams supply irrigation water for rural livelihoods (Nüsser and Schmidt, 2017). The labour-intensive work of constructing and maintaining gravity-fed irrigation canals is done by jirga, traditional community associations. As glaciers retreat due to climate change, water sources at the edge of glaciers have been impacted, reducing water available for irrigation. In response, villagers constructed new channels accessing more distant water for irrigation needs (Parveen et al., 2015). The Aga Khan Development Network (AKDN) supported this substantial task by providing funding and developing a new kind of cross-scale governance network, drawing on local residents for staff (Walter, 2014), and strengthening community resources, training and networks. Challenges remain, including the potential for increased rainfall causing landslides that could damage new canals, and possible expansion of Pakistan’s hydropower infrastructure that would further diminish water resources and displace villages (Shaikh et al., 2015). On a geopolitical scale, decreased water supplies from the glaciers could exacerbate tensions over water resources in the region, impacting water management in many parts of the Indus watershed (Uprety and Salman, 2011; Jamir, 2016; see Section 2.3.1.4 for details). Case Study 3 — Coastal Governance: Risk management for sea level changes in the City of Cape Town, South Africa. Sea-level rise and coastal flooding are the focus of the City of Cape Town’s coastal climate adaptation efforts. The Milnerton coastline High Water Mark, a non-static line marking the high tide, is creating a governance conflict by moving landwards (due to sea level rise) and intersecting with private property boundaries, threatening public beaches and the dune cordon, and placing private property and municipal infrastructure at risk in storm conditions (Sowman et al., 2016). Private property owners are using a mixture of formal, ad hoc, and in some cases illegal, coastal barrier measures to protect their assets from sea level and storm risks, but these are creating additional erosion impacts on the coastline. Legally, the City of Cape Town is not responsible for remediating private land impacted by coastal erosion (Smith et al., 2016). However, city officials feel compelled to take action for the common good using a progressive, multistakeholder participatory approach. This involves opening up opportunities for dialogue and co-producing knowledge, instead of a purely legalistic and state-centric compliance approach (Colenbrander et al., 2015). The city’s actions are both mindful of international frameworks on climate change and responsive to national and provincial legislation and policy. A major challenge that remains is how to navigate the power struggles that will be triggered by this consultative process, as different actors define and negotiate their interests, roles and responsibilities (see Section 4.4.3; Table 4.9). Conclusions These cases illustrate four important points. First, new governance challenges are emerging due to climate change, including: disruptions to long-established cultures, livelihoods and even territorial sovereignty (Case 1); changes in the accessibility and availability of vital resources (Case 2); and the blurring of public and private boundaries of risk and responsibility through accelerated coastal erosion (Case 3; Figure CB3.1). Second, new governance arrangements are emerging to address these challenges, including participatory and networked structures linking formal and informal networks, and involving state, private sector, indigenous and civil society actors in different configurations (Figure CB3.2). Third, climate governance is a complex, contested and unfolding process, with governance actors and networks having to learn from experience, to innovate and develop context-relevant arrangements that can be adjusted in the face of ongoing change. Lastly, there is no single climate governance panacea for the ocean, coasts and cryosphere. Empirical evidence on which governance arrangements work well in which context is still limited, but ‘good governance’ norms indicate the importance of inclusivity, fairness, deliberation, reflexivity, responsiveness, social learning, the co-production of knowledge, and respect for ethnic and cultural diversity. [END CROSS-CHAPTER BOX 3 HERE] 1.8 Knowledge Systems for Understanding and Responding to Change Assessments of how climate change interacts with the planet and people are largely based on scientific knowledge from observations, theories, modelling and synthesis to understand physical and ecological systems (Section 1.8.1), societies (e.g., Cross-Chapter Box 2 in Chapter 1, Section 1.5) and institutions (e.g., Cross-Chapter Box 3 in Chapter 1). However, humans integrate information from multiple sources to observe and interact with their environment, respond to changes, and solve problems. Accordingly, SROCC Subject to Copyedit 1-32 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere also recognises the importance of Indigenous knowledge and local knowledge in understanding and responding to changes in the ocean and cryosphere (Sections 1.8.2, 1.8.3; Cross-Chapter Box 4 in Chapter 1). 1.8.1 1.8.1.1 Scientific Knowledge Ocean and Cryosphere Observations Long-term sustained observations are critical for detecting and understanding the processes of ocean and cryosphere change (Rhein et al., 2013; Vaughan et al., 2013). Scientific knowledge of the ocean and cryosphere has increased through time and geographical space (Figure 1.3). In situ ocean subsurface temperature and salinity observations have increased in spatial and temporal coverage since the middle of the 19th century (Abraham et al., 2013), and near global coverage (60°S-60°N) of the upper 2000 metres has been achieved since 2007 due to the international Argo network (Riser et al., 2016; Figure 1.3). Improved data quality and data analysis techniques have reduced uncertainties in global ocean heat uptake estimates (Sections 1.4.1, 5.2.2). In addition to providing deep ocean measurements, repeated hydrographic physical and biogeochemical observations since AR5 have led to improved estimates of ocean carbon uptake and ocean deoxygenation (Sections 1.4.1, 5.2.2.3, 5.2.2.4). Targeted observational programs have improved scientific knowledge for specific regions and physical processes of particular concern in a warming climate, including the Greenland and West Antarctic ice sheets (Section 3.3), and the Atlantic Meridional Overturning Circulation (AMOC) (Section 6.7). Ocean and cryosphere mass changes and sea level studies have benefited from sustained or newly-implemented satellite-based remote sensing technologies, complemented by in situ data such as tide gauges measurements (Sections 3.3, 4.2; Dowell et al., 2013; Raup et al., 2015; PSMSL, 2016). Glacier length measurements in some locations go back many centuries (Figure 1.3), but it is the systematic high-resolution satellite monitoring of a large number of the world’s glaciers since the late 1970s that has improved global assessments of glacier mass loss (Sections 2.2.3, 3.3.2). Limitations in knowledge of ocean and cryosphere change remain, creating knowledge gaps for the SROCC assessment. Ocean and cryosphere datasets are frequently short, and do not always span the key IPCC assessment time intervals (Cross-Chapter Box 1 in Chapter 1), so for many parameters the full magnitude of changes since the pre-industrial period is not observed (Figure 1.3). The brevity of ocean and cryosphere measurements also means that some expected changes cannot yet be detected with confidence in direct observations (e.g., Antarctic sea ice loss in Section 3.2.1, AMOC weakening in Section 6.7.1), or other observed changes cannot yet be robustly attributed to anthropogenic factors (e.g., ice sheet mass loss in Section 3.3.1). Observations for many key ocean variables (Bojinski et al., 2014), such as ocean currents, surface heat fluxes, oxygen, inorganic carbon, subsurface salinity, phytoplankton biomass and diversity, etc., do not yet have global coverage or have not reached the required density or accuracy for detection of change. Some ocean and cryosphere areas remain difficult to observe systematically, e.g. the ocean under sea ice, subsurface permafrost, high mountain areas, marginal seas, coastal areas (Section 4.2.2.3) and ocean boundary currents (Hu and Sprintall, 2016), basin interconnections (Section 6.6), and the Southern Ocean (Sections 3.2, 5.2.2). Measurements that reflect ecosystem change are often location or species specific, and assessments of long-term ocean ecosystem changes are currently only feasible for a limited subset of variables, for example coral reef health (e.g., coral reef health) (Section 5.3; Miloslavich et al., 2018). The deep ocean below 2000 metres is still rarely observed (Talley et al., 2016), limiting (for example) the accurate estimate of deep ocean heat uptake and, consequently the full magnitude of Earth’s energy imbalance (e.g., von Schuckmann et al., 2016; Johnson et al., 2018; Sections 1.2, 1.4, 5.2.2). 1.8.1.2 Reanalysis Products Advances have been made over the past decade in developing more reliable and more highly resolved ocean and atmosphere reanalysis products. Reanalysis products combine observational data with numerical models through data assimilation to produce physically consistent, and spatially complete ocean and climate products (Balmaseda et al., 2015; Lellouche et al., 2018; Storto et al., 2018; Zuo et al., 2018). Ocean reanalyses are widely used to understand changes in physical properties (Section 3.2.1, 5.2), extremes (Sections 6.3 to 6.6), circulation (Section 6.6, 6.7), and to provide climate diagnostics (Wunsch et al., 2009; Balmaseda et al., 2013; Hu and Sprintall, 2016; Carton et al., 2018). Reanalysis products are used in SROCC for assessing climate change process that cause changes in the ocean and cryosphere (e.g., Sections 2.2.1, Subject to Copyedit 1-33 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere 3.2.1, 3.3.1, 3.4.1, 5.2.2, 6.3.1, 6.6.1, 6.7.1). Improvements in reanalysis products provide more realistic forcing for regional models, which are used for assessing regional ocean and cryosphere changes that cannot be resolved in global-scale models (e.g., Section 2.2.1; Mazloff et al., 2010; Fenty et al., 2017). The weather forecasts, and seasonal to decadal predictions building on reanalysis products have important applications in the early warning systems that reduce risk and aid human adaptation to extreme events (Sections 6.3.4, 6.4.3, 6.5.3, 6.7.3, 6.8.5). 1.8.1.3 Model Simulation Data Models are numerical approximations of the Earth system that allow hypotheses about the mechanisms of ocean and cryosphere change to be tested, support attribution of observed changes to specific forcings (Section 1.3), and are the best available information for assessing future change (Figure 1.3). General Circulation Models (GCMs) typically simulate the atmosphere, ocean, sea ice, and land surface, and sometimes also incorporate terrestrial and marine ecosystems. Earth System Models (ESM) are climate models that explicitly include the carbon cycle and may include additional components (e.g., atmospheric chemistry, ice sheets, dynamic vegetation, nitrogen cycle, but also urban or crop models). The systematic set of global-scale model experiments (Taylor et al., 2012) used in SROCC were produced by CMIP5 (CrossChapter Box 1 in Chapter 1), including both GCMs and ESMs. Models may differ in their spatial resolution, and in the extent to which processes are explicitly represented or approximated (parameterised). Model output can be biased due to uncertainties in their physical equations or parameterisations, specification of initial conditions, knowledge of external forcing factors, and unaccounted processes and feedbacks (Hawkins and Sutton, 2009; Deser et al., 2012; Gupta et al., 2013; Lin et al., 2016). Since AR5 there have been advances in modelling the dynamical processes of the Greenland and Antarctica ice sheets, leading to better representation of the range of potential future sea level rise scenarios (Sections 4.2.3). Downscaling, including the use of regional models, makes it possible to improve the spatial resolution of model output in order to better resolve past and future climate change in specific areas, such as high mountains and coastal seas (e.g. Sections 2.2.2, 3.2.3, 3.5.4, 4.2.2, 6.3.1). For biological processes, such as nutrient levels and organic matter production, model uncertainty at regional scales is the main issue limiting confidence in future projections (Sections 5.3, 5.7). While model projections of range shifts for fishes agree with theory and observations, at a regional scale there are known deficiencies in the ways models represent the impacts of ocean variables such as temperature and productivity (Sections 5.2.3, 5.7). 1.8.1.4 Palaeoclimate Data Palaeoclimate data provide a way to establish the nature of ocean and cryosphere changes prior to direct measurements (Figure 1.3), including natural variability and early anthropogenic climate change (MassonDelmotte et al., 2013; Abram et al., 2016). Palaeoclimate records utilise the accumulation of physical, chemical or biological properties within natural archives that are related to climate at the time the archive formed. Commonly used palaeoclimate evidence for ocean and cryosphere change comes from marine and lake sediments, ice layers and bubbles, tree growth rings, past shorelines and shallow reef deposits. In many mountain areas, centuries to millennia of palaeoclimate information is now being lost through widespread melting of glacier ice (Cross-Chapter Box 6 in Chapter 2). Palaeoclimate data are spatially limited (Figure 1.3), but often represent regional to global-scale climate patterns, either individually or as syntheses of networks of data (PAGES2K Consortium, 2017). Palaeoclimate data provide evidence for multi-metre global sea level rises and shifts in climate zones and ocean ecosystems during past warm climate states where temperatures were similar to those expected later this century (Hansen et al., 2016; Fischer et al., 2018; Section 4.2.2). Palaeoclimate reconstructions give context to recent ocean and cryosphere changes that are unusual in the context of variability over past centuries to millennia, including acceleration in Greenland and Antarctic Peninsula ice melt (Section 3.3.1), declining Arctic sea ice (Section 3.2.1), and emerging evidence for a slowdown of AMOC (Section 6.7.1). Assessments of climate model performance across a wider-range of climate states than is possible using direct observations alone also draws on palaeoclimate data (Flato et al., 2013), and since AR5 important progress has been made to calibrate modelled ice sheet processes and future sea level rise based on palaeoclimate evidence (Cross-Chapter Box 8 in Chapter 3). Subject to Copyedit 1-34 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Figure 1.3: Illustrative examples of the availability of ocean and cryosphere data relative to the major time periods assessed in SROCC. Upper panel; observed (Keeling et al., 1976) and reconstructed (Bereiter et al., 2015) atmospheric carbon dioxide (CO2) concentrations, as well as the Representative Concentration Pathways (RCP) of CO2 for low (RCP2.6) and high (RCP8.5) future emission scenarios (van Vuuren et al., 2011a; Cross-chapter box 1 in Chapter 1). Lower panel; illustrative examples of data availability for the ocean and cryosphere (Section 1.8.1; Taylor et al., 2012; Boyer et al., 2013; Dowell et al., 2013; McQuatters-Gollop et al., 2015; Raup et al., 2015; Olsen et al., 2016; PSMSL, 2016; PAGES2K Consortium, 2017; WGMS, 2017). The amount of data available through time is shown by the heights of the time series for observational data, palaeoclimate data and model simulations, expressed relative to the maximum annual data availability (maximum values given on plot; M = million, k = thousand). Spatial coverage of data across the globe or the relevant domain is shown by colour scale. See SM1.4 for further details. 1.8.2 Indigenous Knowledge and Local Knowledge Humans create, use, and adapt knowledge systems to interact with their environment (Agrawal, 1995; Escobar, 2001; Sillitoe, 2007), and to observe and respond to change (Huntington, 2000; Gearheard et al., Subject to Copyedit 1-35 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere 2013; Maldonado et al., 2016; Yeh, 2016). Indigenous knowledge (IK) refers to the understandings, skills, and philosophies developed by societies with long histories of interaction with their natural surroundings. It is passed on from generation to generation, flexible, and adaptive in changing conditions, and increasingly challenged in the context of contemporary climate change. Local knowledge (LK) is what non-Indigenous communities, both rural and urban, use on a daily and lifelong basis. It is multi-generational, embedded in community practices and cultures, and adaptive to changing conditions (FAO, 2018). Each chapter of SROCC cites examples of IK and LK related to ocean and cryosphere change. IK and LK stand on their own, and also enrich and complement each other and scientific knowledge. For example, Australian Aboriginal groups’ Indigenous oral history provides empirical corroboration of the sea level rise 7,000 years ago (Nunn and Reid, 2016), and their seasonal calendars direct hunting, fishing, planting, conservation, and detection of unusual changes today (Green et al., 2010). LK works in tandem with scientific knowledge, for example, as coastal Australian communities consider the impacts and tradeoffs of sea-level rise (O'Neill and Graham, 2016). Both IK and LK are increasingly used in climate change research and policy efforts to engage affected communities to facilitate site-specific understandings of, and responses to, the local effects of climate change (Hiwasaki et al., 2014; Hou et al., 2017; Mekonnen et al., 2017). IK and LK enrich climate-resilient development pathways, particularly by engaging multiple stakeholders and the diversity of socio-economic, cultural, and linguistic contexts of populations affected by changes in the ocean and cryosphere (CrossChapter Box 4 in Chapter 1). Global environmental assessments increasingly recognise the importance of IK and LK (Thaman et al., 2013; Beck et al., 2014; Díaz et al., 2015). References to IK in IPCC assessment reports increased 60% from AR4 to AR5, and highlighted the exposures and vulnerabilities of Indigenous populations to climate change risks related to socio-economic status, resource-based dependence, and geographic location (Ford et al., 2016a). All four assessments of the 2018 Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES, 2018a; IPBES, 2018b; IPBES, 2018c; IPBES, 2018d) engaged IK and LK (Díaz et al., 2015; Roué and Molnar, 2017; Díaz et al., 2018). Peer-reviewed research on IK and LK is burgeoning (Savo et al., 2016), providing information that can guide responses and inform policy (Huntington, 2011; Nakashima et al., 2012; Lavrillier and Gabyshev, 2018). However, most global assessments still fail to incorporate ‘the plurality and heterogeneity of worldviews’ (Obermeister, 2017), resulting ‘in a partial understanding of core issues that limits the potential for locally and culturally appropriate adaptation responses’ (Ford et al., 2016b). IK and LK provide case-specific information that may not be easily extrapolated to the scales of disturbance that humans exert on natural systems (Wohling, 2009). Some forms of IK and LK are also not amenable to being captured in peer-reviewed articles or published reports, and efforts to translate IK and LK into qualitative or quantitative data may mute the multidimensional, dynamic, and nuanced features that give IK and LK meaning (DeWalt, 1994; Roncoli et al., 2009; Goldman and Lovell, 2017). Nonetheless, efforts to collaborate with IK and LK knowledge holders (Baptiste et al., 2017; Karki et al., 2017; Lavrillier and Gabyshev, 2017; Roué et al., 2017; David-Chavez and Gavin, 2018) and to systematically assess published IK and LK literature in parallel with scientific knowledge result in increasingly effective usage of the multiple knowledge systems to better characterise and address ocean and cryosphere change (Huntington et al., 2017; Nalau et al., 2018; Ford et al., 2019). [START CROSS-CHAPTER BOX 4 HERE] Cross-Chapter Box 4: Indigenous Knowledge and Local Knowledge in Ocean and Cryosphere Change Authors: Susan Crate (USA), William Cheung (Canada), Bruce Glavovic (New Zealand), Sherilee Harper (Canada), Hélène Jacot Des Combes (Fiji/France), Monica Ell Kanayuk (Canada), Ben Orlove (USA), Joanna Petrasek MacDonald (Canada), Anjal Prakash (Nepal/India), Jake Rice (Canada), Pasang Yangjee Sherpa (Nepal), Martin Sommerkorn (Norway/Germany) Introduction Subject to Copyedit 1-36 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere This Cross-Chapter Box describes how Indigenous knowledge (IK) and local knowledge (LK) are different and unique sources of knowledge, which are critical to observing, responding to, and governing the ocean and cryosphere in a changing climate (See SROCC Annex I: Glossary for definitions). International organisations recognise the importance of IK and LK in global assessments, including UN Environment, UNDP, UNESCO, IPBES, and the World Bank. IK and LK are referenced throughout SROCC, understanding that many climate change impacts affect, and will require responses from, local communities (both Indigenous and non-Indigenous) who maintain a close connection with the ocean and/or cryosphere. Attention to IK and LK in understanding global change is relatively recent, but important (high confidence). For instance, in 1980, Alaskan Inuit formed the Alaska Eskimo Whaling Commission (AEWC) in response to the International Whaling Commission’s science that underestimated the Bowhead whale population and, in 1977, banned whaling as a result (Huntington, 1992). The AEWC facilitated an improved population count using a study design based on IK, which indicated a harvestable population (Huntington, 2000). There are various approaches for utilising multiple knowledge systems. For example, the Mi’kmaw Elders’ concept of Two Eyed Seeing: which is ‘learning to see from one eye with the strengths of Indigenous knowledges, and from the other eye with the strengths of Western [scientific] knowledges, and to use both together, for the benefit of all’ (Bartlett et al., 2012), to preserve the distinctiveness of each, while allowing for fuller understandings and actions (Bartlett et al., 2012: 334). Knowledge Co-production Scientific knowledge, Indigenous knowledge, and local knowledge can complement one another by engaging both quantitative data and qualitative information, including people’s observations, responses, and values (Huntington, 2000; Crate and Fedorov, 2013; Burnham et al., 2016; Figure CB4.1). However, this process of knowledge co-production is complex (Jasanoff, 2004) and IK and LK possess uncertainties of a different nature from those of scientific knowledge (Kahneman and Egan, 2011), often resulting in the dominance of scientific knowledge over IK and LK in policy, governance, and management (Mistry and Berardi, 2016). Working across disciplines (interdisciplinarity; Strang, 2009), and/or engaging multiple stakeholders (transdisciplinarity; Klenk and Meehan, 2015; Crate et al., 2017), are approaches used to bridge knowledge systems. The use of all knowledge relevant to a specific challenge can involve approaches such as: scenario building across stakeholder groups to capture the multiple ways people perceive their environment and act within it (Klenk and Meehan, 2015); knowledge co-production to achieve collaborative management efforts (Armitage et al., 2011); and working with communities to identify shared values and perceptions that enable context-specific adaptation strategies (Grunblatt and Alessa, 2017). Broad stakeholder engagement, including affected communities, Indigenous Peoples, local and regional representatives, policy makers, managers, interest groups, and organisations, has the potential to effectively utilise all relevant knowledge (Obermeister, 2017), and produce results that reduce the disproportionate influence that formally educated and economically advantaged groups often exert in scientific assessments (Castree et al., 2014). Subject to Copyedit 1-37 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Figure CB4.1: Knowledge co-production using scientific knowledge, Indigenous knowledge and/or local knowledge to create new understandings for decision making. Panels A, B, and C represent the use of one, two, and three knowledge systems, respectively, illustrating co-production moments in time (collars). Panel A represents a context which uses one knowledge system, for example, of Indigenous knowledge used by Indigenous peoples; or of the local knowledge used by farmers, fishers, and rural or urban inhabitants; or of scientific knowledge used in contexts where substantial human presence is lacking. Panel B depicts the use of two knowledge systems, as described in this Cross-Chapter Box in the case of Bowhead whale population counts and in Himalayan flood management. Panel C illustrates the use of all three knowledge systems, as in the Pacific case in this Cross-Chapter Box. Each collar represents how making use of knowledge from different systems is a matter of both identifying available knowledge across systems and of knowledge holder deliberations. In these processes, learning takes place on how to relate knowledge from different systems for the purpose of improved decisions and solutions. Knowledge from different systems can enrich the body of relevant knowledge while continuing independently, or can be combined to co-produce new knowledge. Contributions to SROCC Observations, responses, and governance are three important contributions that IK and LK make in ocean and cryosphere change: Observations: IK and LK observations document glacier and sea ice dynamics, permafrost dynamics, coastal processes, etc. (Sections 2.3.2.2.2, 2.5, 3.2.2, 3.4.1.1, 3.4.1.1, 3.4.1.2, 4.3.2.4.2, 5.2.3 and Box 2.4), and how they interact with social-cultural factors (West and Hovelsrud, 2010). Researchers have begun documenting IK and LK observations only recently (Sections 2.3.1.1, 3.2, 3.4, 3.5, Box 4.4, 5.4.2.2.1). Responses: Either IK or LK alone (Yager, 2015), or used with scientific knowledge (Nüsser and Schmidt, 2017) inform responses (Sections 2.3.1.3.2, 2.3.2.2.2, 3.5.2, 3.5.4, 4.4.2, Box 4.4, 5.5.2, 6.8.4, 6.9.2). Utilising multiple knowledge systems requires continued development, accumulation, and transmission of LK and IK and scientific knowledge towards understanding the ecological and cultural context of diverse peoples (Crate and Fedorov, 2013; Jones et al., 2016), resulting in the incorporation of relevant priorities and contexts into adaptation responses (Sections 3.5.2, 3.5.4, 4.4.4, 5.5.2, 6.8.4, 6.9.2, Box 2.3). Governance: Utilising IK and LK in climate decision- and policy-making includes customary Indigenous and local institutions (Karlsson and Hovelsrud, 2015), as in the case when Indigenous communities are engaged in an integrated approach for disaster risk reduction in response to cryosphere hazards (Carey et al., 2015). The effective engagement of communities and stakeholders in decisions requires using the multiple knowledge systems available (Chilisa, 2011; Sections 2.3.1.3.2`, 2.3.2.3`, 3.5.4`, 4.4.4`, Ch 4 Table 4`, 5.5.2`, 6.8.4`, 6.9.2`; Sections 2.3.1.3.2`, 2.3.2.3`, 3.5.4`, 4.4.4`, Ch 4 Table 4.9`, 5.5.2`, 6.8.4`, 6.9.2). Subject to Copyedit 1-38 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Examples from regions covered in this report IK and LK in the Pacific: Historically, Pacific communities, who depend on marine resources for essential protein (Pratchett et al., 2011), use LK for management systems to determine access to, and closure of, fishing grounds, the latter to respect community deaths, sacred sites, and customary feasts. Today a hybrid system, Locally Managed Marine Protected Areas (LMMAs), is common and integrates local governance with NGO or government agency interventions (Jupiter et al., 2014). The expected benefits of these management systems support climate change adaptation through sustainable resource management (Roberts et al., 2017) and mitigation through improved carbon storage (Vierros, 2017). The challenges to wider use include both how to upscale LMMAs (Roberts et al., 2017; Vierros, 2017), and how to assess them as climate change adaptation and mitigation solutions (Rohe et al., 2017; Section 5.4). IK and Pikialasorsuaq: Pikialasorsuaq (North Water Polynya), in Baffin Bay, is the Arctic’s largest polynya, or area of open water surrounded by ice, and is also one of the most biologically productive regions in the Arctic (Barber et al., 2001). Adjacent Inuit communities depend on Pikialasorsuaq for their food security and subsistence economy (Hastrup et al., 2018). They use Qaujimajatuqangit, an IK system, in daily and seasonal activities (ICC, 2017). The sea-ice bridge north of the Pikialasorsuaq is no longer forming as reliably as in the past, resulting in a polynya that is geographically and seasonally less defined (Ryan and Münchow, 2017). In response, the Inuit Circumpolar Council initiated the Pikialasorsuaq Commission who formed an Inuit-led management authority to (1) oversee monitoring and research to conserve the polynya’s living resources; (2) identify an Indigenous Protected Area, to include the polynya and dependent communities; and (3) establish a free travel zone for Inuit across the Pikialasorsuaq region (ICC, 2017; Box 3.2). LK in the Alps: Mountain guides and other local residents engaged in supporting mountain tourism draw on LK for livelihood management. A study at Mont Blanc lists specific cryosphere changes which they have observed, including glacial shrinkage, reduction in ice and snow cover. As a result, the categorisation of the difficulty of a number of routes has changed, and the timing of the climbing season has shifted earlier (Mourey and Ravanel, 2017; Section 2.3.5). LK to Manage Flooding: Climate change is increasing glacial meltwater and rain-induced disasters in the Himalayan region and affected communities in China, Nepal, and India use LK to adapt (Nadeem et al., 2012). For instance, rains upstream in Gandaki (Nepal) flood downstream areas of Bihar, India. Local communities’ knowledge of forecasting floods has evolved over time through the complexities of caste, class, gender, and ecological flux, and is critical to flood forecasting and disaster risk reduction. Local communities manage risk by using a diverse set of knowledge, including phenomenological (e.g., river sound), ecological (e.g., red ant movement), and riverine (e.g., river colour) indicators, alongside meteorological and official information (Acharya and Prakash, 2018; Section 2.3.2.3). Knowledge Holders’ Recommendations for Utilising IK and LK in Assessment Reports Perspectives from the Himalayas: IK and LK holders in the Himalayas have conducted long-term systematic observations in these remote areas for centuries. Contemporary IK details change in phenology, weather patterns, and flora and fauna species, which enriches scientific knowledge of glacial retreat and potential glacial lake outbursts (Sherpa, 2014). The scientific community can close many knowledge gaps by engaging IK and LK holders as counterparts. Suggestions towards this objective are: work with affected communities to elicit their knowledge of change, especially IK and LK holders with more specialised knowledge (farmers, herders, mountain guides, etc.), and use location- and culture-specific approaches to share scientific knowledge and utilise it with IK and LK. Perspectives from the Inuit Circumpolar Council (ICC), Canada: Engaging Inuit as partners across all climate research disciplines ensures that Inuit knowledge and priorities guide research, monitoring, and the reporting of results in Inuit homeland. Doing so enhances the effectiveness, impact, and usefulness of global assessments, and ensures that Inuit knowledge is appropriately reported in assessments. Inuit seek to achieve self-determination in all aspects of research carried out in Inuit homeland (e.g., Nickels et al., 2005). Inuit actively produce and utilise climate research (e.g., ITK, 2005; ICC, 2015) and lead approaches to address climate challenges spurred by great incentive to develop innovative solutions. Engaging Inuit representative organisations and governments as partners in research recognises that the best available knowledge includes IK, enabling more robust climate research that in turn informs climate policy. When interpreted and applied properly, IK comes directly from research by Inuit and from an Inuit perspective (ICC, 2018). This can be Subject to Copyedit 1-39 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere achieved by working with Inuit on scoping and methodology for assessments and supporting inclusion of Inuit experts in research, analysis, and results dissemination. [END CROSS-CHAPTER BOX 4 HERE] 1.8.3 The Role of Knowledge in People’s Responses to Climate, Ocean and Cryosphere Change To hold global average temperature to well below 2 °C above pre-industrial levels, substantial changes in the day-to-day activities of individuals, families, communities, the private sector, and governance bodies will be required (Ostrom, 2010; Creutzig et al., 2018). Enabling these changes at a meaningful societal scale requires sensitivity to communities and their use of multiple knowledge systems to best motivate effective responses to the risks and opportunities posed by climate change (medium confidence) (1.8.2, Cross-Chapter Box 4 in Chapter 1). Meaningful engagement of people and communities with climate change information depends on that information cohering with their perception of how the world works (Crate and Fedorov, 2013). The values and identities people hold affect how acceptable they find the behavioural changes, technological solutions and governance that climate change action requires (Moser, 2016). Education and climate literacy contribute to climate change action and adaptation (high confidence). Although public understanding of humanity’s role in both causing and abating climate change has increased in the last decade (Milfont et al., 2017), levels of climate concern vary greatly globally (Lee et al., 2015). Educational attainment has the strongest effect on raising climate change awareness (Lee et al., 2015), and research documents the value of evidence-based climate change education, particularly during formal schooling (Motta, 2018). People further understand climate change as a serious threat when they experience it in their lives and have knowledge of its human causes (Lee et al., 2015; Shi et al., 2016). Education and tailored climate communication strategies that are respectful of people’s values and identity can aid acceptance and implementation of the local to global-scale approaches and policies required for effective climate change mitigation and adaptation (Shi et al., 2016; Anisimov and Orttung, 2018; Sections 3.5.4, 4.4), while also supporting climate-resilient development pathways (see also Cross-Chapter Box 2 in Chapter 1, and FAQ1.2). Human psychology complicates engagement with climate change, due to complex social factors, including values (Corner et al., 2014), identity (Unsworth and Fielding, 2014), ideology (Smith and Mayer, 2019), and the framing of climate messaging. Additionally, psychology effects adaptation actions, motivated by perceptions that others are already adapting, avoidance of an unpleasant state of mind, feelings of selfefficacy, and belief in the efficacy of the adaptation action (van Valkengoed and Steg, 2019). Better understandings of the psychological implications, across diverse communities and social and political contexts, will facilitate a just transition of both emissions reduction and adaptation (Schlosberg et al., 2017). Impacts of climate change on natural and human environments (e.g., extreme weather) or human-caused modifications to the environment (e.g., adaptation) will raise further psychological challenges. This includes psychological impacts to the emotional wellbeing of people adversely affected by climate change (Ogunbode et al., 2018), resulting in solastalgia (Albrecht et al., 2007), a distress akin to homesickness while in their home environment (McNamara and Westoby, 2011). 1.9 1.9.1 Approaches Taken in this Special Report Methodologies Relevant to this Report SROCC assesses literature on ocean and cryosphere change and associated impacts and responses, focusing on advances in knowledge since AR5. The literature used is primarily published, peer-reviewed scientific, social science and humanities research. In some cases, grey-literature sources (for example, published reports from governments, industry, research institutes, and non-government organisations) are used where there are important gaps in available peer-reviewed literature. It is recognised that published knowledge from many parts of the world most vulnerable to ocean and cryosphere change is still limited (Czerniewicz et al., 2017). Subject to Copyedit 1-40 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Where possible, SROCC draws upon established methodologies and/or frameworks. Cross-Chapter Boxes in Chapter 1 address methodologies used for projections of future change (Cross-Chapter Box 1 in Chapter 1), for assessing and reducing risk (Cross-Chapter Box 2 in Chapter 1), for governance options relevant to a problem or region (Cross-Chapter Box 3 in Chapter 1), and for utilising Indigenous knowledge and local knowledge (Cross-Chapter Box 4 in Chapter 1). It is recognised in the assessment process that multiple and non-static factors determine human vulnerabilities to climate change impacts, and that ecosystems provide essential services that have both commercial and non-commercial value (Section 1.5). Economic methods are also important in SROCC, for estimating the economic value of natural systems, and for aiding decisionmaking around mitigation and adaptation strategies (Section 1.6). 1.9.2 Communication of Confidence in Assessment Findings SROCC uses calibrated language for the communication of confidence in the assessment process (Mastrandrea et al., 2010; Mach et al., 2017). Calibrated language is designed to consistently evaluate and communicate uncertainties that arise from incomplete knowledge due to a lack of information, or from disagreement about what is known or even knowable. The IPCC calibrated language uses qualitative expressions of confidence based on the robustness of evidence for a finding, and (where possible) uses quantitative expressions to describe the likelihood of a finding (Figure 1.4). Qualitative expressions (confidence scale) describe the validity of a finding based on the type, amount, quality and consistency of evidence, and the degree of agreement between different lines of evidence (Figure 1.4, step 2). Evidence includes all knowledge sources, including IK and LK where available. Very high and high confidence findings are those that are supported by multiple lines of robust evidence with high agreement. Low or very low confidence describe findings for which there is limited evidence and/or low agreement among different lines of evidence, and are only presented in SROCC if they address a major topic of concern. Quantitative expressions (likelihood scale) are used when sufficient data and confidence exists for findings to be assigned a quantitative or probabilistic estimate (Figure 1.4, step 3). In the scientific literature, a finding is often said to be significant if it has a likelihood exceeding 95% confidence. Using calibrated IPCC language, this level of statistical confidence would be termed extremely likely. Lower levels of likelihood than those derived numerically can be assigned by expert judgement to take into account structural or measurement uncertainties within the products or data used to determine the probabilistic estimates (e.g. Table CB1.1). Likelihood statements may be used to describe how climate changes relate to the ends of distribution functions, such as in detection and attribution studies that assess the likelihood that an observed climate change or event is different to a reference climate state (Section 1.3). In other situations likelihood statements refer to the central region across a distribution of possibilities. Examples are the estimates of future changes based on large ensembles of climate model simulations, where the central 66% of estimates across the ensemble (i.e., the 17–83% range) would be termed a likely range (Figure 1.4, step 3). It is increasingly recognised that effective risk management requires assessments not just of ‘what is most likely’ but also of ‘how bad things could get’ (Mach et al., 2017; Weaver et al., 2017; Xu and Ramanathan, 2017; Spratt and Dunlop, 2018; Sutton, 2018). In response to the need to reframe policy-relevant assessments according to risk (Section 1.5; Mach et al., 2016; Weaver et al., 2017; Sutton, 2018), an effort is made in SROCC to report on potential changes for which there is low scientific confidence or a low likelihood of occurrence, but that would have large impacts if realised (Mach et al., 2017). In some cases where evidence is limited or emerging, phenomena may instead be discussed according to physically plausible scenarios of impact (e.g., Table 6.1). In some cases, deep uncertainty (Cross-Chapter Box 5 in Chapter 1) may exist in current scientific assessments of the processes, rate, timing, magnitude, and consequences of future ocean and cryosphere changes. This includes physically plausible high-impact changes, such as high-end sea level rise scenarios that would be costly if realised without effective adaptation planning and even then may exceed limits to adaptation. Means such as expert judgement, scenario-building, and invoking multiple lines of evidence enable comprehensive risk assessments even in cases of uncertain future ocean and cryosphere changes. Subject to Copyedit 1-41 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Figure 1.4: Schematic of the IPCC usage of calibrated language, with examples of confidence and likelihood statements from this report. Figure developed after Mastrandrea et al. (2010), Mach et al. (2017) and Sutton (2018). [START CROSS-CHAPTER BOX 5 HERE]. Subject to Copyedit 1-42 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Cross-Chapter Box 5: Confidence and Deep Uncertainty Authors: Carolina Adler (Switzerland/Australia), Michael Oppenheimer (USA), Nerilie Abram (Australia), Kathleen McInnes (Australia) and Ted Schuur (USA) Definition and Context Characterising, assessing and managing risks to climate change involves dealing with inherent uncertainties. Uncertainties can lead to complex decision-making situations for managers and policy-makers tasked with risk management, particularly where decisions relate to possibilities assessed as having low or unknown confidence/likelihood, yet would have high impacts if realised. While uncertainty can be quantitatively or qualitatively assessed (Section 1.9.2; Figure 1.4), a situation of deep uncertainty exists when experts or stakeholders do not know or cannot agree on: (1) appropriate conceptual models that describe relationships among key driving forces in a system; (2) the probability distributions used to represent uncertainty about key variables and parameters; and/or, (3) how to weigh and value desirable alternative outcomes (adapted from Lempert et al., 2003; Marchau et al., 2019b). The concept of deep uncertainty has been debated and addressed in the literature for some time, with diverse terminology used. Terms such as great uncertainty (Hansson and Hirsch Hadorn, 2017), contested uncertain knowledge (Douglas and Wildavsky, 1983), ambiguity (Ellsberg, 1961), and Knightian uncertainty (Knight, 1921), among others, are also present in the literature to refer to the multiple components of uncertainty that need to be accounted for in decision making. The purpose of this Cross-Chapter Box is to constructively engage with the concept of deep uncertainty, by first providing some context for how the IPCC has dealt with deep uncertainty in the past. This is followed by examples of cases from the ocean and cryosphere assessments in SROCC, where deep uncertainty has been addressed to advance assessment of risks and their management. How has the IPCC and other literature dealt with deep uncertainty? The IPCC assessment process provides instances of how deep uncertainty can manifest. In assessing the scientific evidence for anthropogenic climate change, and its influence on the Earth system in the past and future, IPCC assessments can identify areas where a large range of possibilities exist in the scientific literature or where knowledge of the underlying processes and responses is lacking. Existing guidelines to ensure consistent treatment of uncertainties by IPCC author teams (Mastrandrea et al., 2010; Section 1.9.2) may not be sufficient to ensure the desired consistency or guide robust findings when conditions of deep uncertainty are present (Adler and Hirsch Hadorn, 2014). The IPCC, and earlier assessments, encountered deep uncertainty when evaluating numerous aspects of the climate change problem. Examining these cases sheds light on approaches to quantifying and reducing deep uncertainty. An assessment by the US National Academy of Sciences (Charney et al., 1979; commonly referred to as the Charney Report) provides a classic example. Evaluating climate sensitivity to a doubling of carbon dioxide concentration, and developing a probability distribution for it, was challenging because only two 3-D climate models and a handful of model variants and realisations were available. The panel invoked three strategies to eliminate some of these simulations: (1) Using multiple lines of evidence to complement the limited model results; (2) estimating the consequences of poor or absent model representations of certain physical processes (particularly cumulus convection, high-altitude cloud formation, and non-cloud entrainment); and, (3) evaluating mismatches between model results and observations. This triage yielded “probable bounds” of 2oC – 3.5oC on climate sensitivity. The panel then invoked expert judgment (Box 12.2 in Collins et al., 2013) to broaden the range to 3±1.5oC, with 3oC referred to as the “most probable value”. The panel did not report its confidence in these judgments. The literature has expanded greatly since, allowing successive IPCC assessments to refine the approach taken in the Charney report. By AR5, four lines of evidence (from instrumental records, paleoclimate data, model inter-comparison of sensitivity, and model-climatology comparisons) were assessed to determine that “Equilibrium climate sensitivity is likely in the range 1.5°C to 4.5°C (high confidence), extremely unlikely less than 1°C (high confidence), and very unlikely greater than 6°C (medium confidence)” (Box 12.2 in Collins et al., 2013). The Charney report began the process of convergence of opinion around a single probability range (essentially, category (2) in the definition of deep uncertainty, above), at least for sensitivity arising from fast feedbacks captured by global climate models (Hansen et al., 2007). Subsequent Subject to Copyedit 1-43 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere assessments increased confidence, eliminating deep uncertainty about this part of the sensitivity problem over a wide range of probability. Cases of Deep Uncertainty from SROCC Case A — Permafrost carbon and greenhouse gas emissions: AR5 reported the estimated size of the organic carbon pool stored frozen in permafrost zone soils, but uncertainty estimates were not available (Tarnocai et al., 2009; Ciais et al., 2013). AR5 further reported that future greenhouse gas emissions (CO2 only) from permafrost were the most uncertain biogeochemical feedback on climate of the ten factors quantified (Figure 6.20 in Ciais et al., 2013). However, the low confidence assigned to permafrost was not due to few studies, but rather to divergence on the conceptual framework relating changes in permafrost carbon and future greenhouse gas emissions, as well as the probability distribution of key variables. Most large-scale carbonclimate models still lack key landscape-level mechanisms that are known to abruptly thaw permafrost and expose organic carbon to decomposition, and many do not include mechanisms needed to differentiate the release of methane versus carbon dioxide with their very different global warming potentials. Studies since AR5 on potential methane release from laboratory soil incubations (Schädel et al., 2016; Knoblauch et al., 2018), actual methane release from the Siberian shallow Arctic ocean shelves (Shakhova et al., 2013; Thornton et al., 2016), changes in permafrost carbon stocks from the Last Glacial Maximum until present (Ciais et al., 2011; Lindgren et al., 2018), and potential carbon uptake by future plant growth (Qian et al., 2010; McGuire et al., 2018) have widened rather than narrowed the uncertainty range (Section 3.4.3.1.1). Accounting for greenhouse gas release from polar and high mountain (Box 2.2) permafrost, introduces an element of deep uncertainty when determining emissions pathways consistent with Article 2 of the Paris Agreement (Comyn-Platt et al., 2018). With stakeholder needs in mind, scientists have been actively engaged in narrowing this uncertainty by using multiple lines of evidence, expert judgment, and joint evaluation of observations and models. As a result, SROCC has reduced uncertainty and introduced confidence assessments across some but not all components of this problem (Section 3.4.3.1.1.). Case B — Antarctic ice sheet and sea level rise: Dynamical ice loss from Antarctica (Cross-Chapter Box 8 in Chapter 3) provides an example of lack of knowledge about processes, and disagreement about appropriate models and probability distributions for representing uncertainty (categories (1) and (2) in the definition of deep uncertainty). AR5 used a statistical model and expert judgment to reduce uncertainty compared to AR4 (Church et al., 2013). Based on modelling of marine ice sheet processes after AR5, SROCC has further reduced uncertainty in the Antarctic contribution to sea level rise. The likely range including the potential contribution of marine ice sheet instability is quantified as 0.02-0.23 m for 2081-2100 (and 0.03-0.28 m for 2100) compared to 1986-2005 under RCP8.5 (medium confidence). However, the magnitude of additional rise beyond 2100, and the probability of greater sea level rise than that included in the likely range before 2100, are characterised by deep uncertainty (Section 4.2.3). Policy makers at various levels of governance are considering adaptation investments (e.g., hard infrastructure, retreat, and nature-based defences) for multi-decadal time horizons that consider projection uncertainty (Sections 4.4.2, 4.4.3). For example, extreme sea levels (e.g., the local “hundred-year flood”) now occurring during storms that are historically rare are projected to become annual events by 2100 or sooner at many low-lying coastal locations (Section 4.4.3). Sea level rise exceeding the likely range, or an alternate pathway to the assumed climate change scenario (e.g., which RCP is used in risk estimation), could alter these projections and both factors are characterised by deep uncertainty. Among the strategies used to reduce deep uncertainty in these cases are formal and informal elicitation of expert judgment to project ice sheet behaviour (Horton et al., 2014; Bamber et al., 2019), and development of plausible sea level rise scenarios, including extreme cases (Sections 4.2.3, 4.4.5.3). Frameworks for risk management under deep uncertainty in the context of time lags between commitment to ice sheet losses and emissions mitigation, and between coastal adaptation planning and implementation, are currently emerging in the literature (Section 4.4.5.3.4). Case C — Compound risks and cascading impacts: Compound risks and cascading impacts (Section 6.1, 6.8, Figure 1.1, Figure 6.1) arise from multiple coincident or sequential hazards (Zscheischler et al., 2018). Compound risks are an example of deep uncertainty because their rarity means that there is often a lack of data or modelling to characterise the risks statistically under present conditions or future changes (Gallina et al., 2016), and there is the potential that climate elements could cross tipping points (e.g., Cai et al., 2016). Nevertheless, effective risk reduction strategies can be developed without knowing the statistical likelihoods Subject to Copyedit 1-44 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere of such events by acknowledging the possibility that an event can occur (Dessai et al., 2009). Such strategies are typically well-hedged against a variety of different futures and adjustable through time in response to emerging information (Lempert et al., 2010). Case studies are useful for raising awareness of the possibility of compound events and provide valuable learnings for decision makers in the form of analogues (McLeman and Hunter, 2010). They can provide a basis for devising scenarios to stress test systems in other regions for the purposes of understanding and reducing risk. The case study describing the ocean, climate and weather events in the Australian state of Tasmania in 2015/2016 (Box 6.1) provides such an example. It led to compound risks that could not have been estimated due to deep uncertainty. The total cost of the cooccurring fires, floods and marine heat wave to the state government was estimated at about $300 million USD, and impacts on the food, energy and manufacturing sectors reduced Tasmania’s anticipated economic growth by approximately half (Eslake, 2016). In the aftermath of this event, the government increased funding to relevant agencies responsible for flood and bushfire management and independent reviews have recommended major policy reforms that are now under consideration (Blake et al., 2017; Tasmanian Climate Change Office, 2017). What can we learn from SROCC cases in addressing deep uncertainty? Using the adapted definition as a framing concept for deep uncertainty (see also Glossary), we find that each of the three cases described in this Cross-Chapter Box involve at least one of the three ways that deep uncertainty can manifest. In Case A, incomplete knowledge on relationships and key drivers and feedbacks (category 1), coupled with broadened probability distributions in post-AR5 literature (category 2), are key reasons for deep uncertainty. In Case B, the inability to characterise the probability of marine ice sheet instability due to a lack of adequate models resulting in divergent views on the probability of ice loss lead to deep uncertainty (categories 1 and 2). In Case C, the Australian example provides insights on the inadequacy of models or previous experience for estimating risk of multiple simultaneous extreme events, contributing to the exhaustion of resources which were then insufficient to meet the need for emergency response. This case also points to the complex task of addressing multiple simultaneous extreme events, and the multiple ways of valuing preferred outcomes in reducing future losses (category 3). The three cases validate the continued iterative process required to meaningfully engage with deep uncertainty in situations of risk, through means such as elicitation, deliberation, and application of expert judgement, scenario-building, and invoking multiple lines of evidence. These approaches demonstrate feasible ways to address or even reduce deep uncertainty in complex decision situations (see also Marchau et al., 2019a), considering that possible obstacles and time investment needed to address deep uncertainty, should not be underestimated. [END CROSS-CHAPTER BOX 5 HERE] 1.10 Integrated Storyline of this Special Report The chapters that follow in this special report are framed around geographies or climatic processes where the ocean and/or cryosphere are particularly important for ecosystems and people. The chapter order follows the movement of water; from Earth’s shrinking mountain and polar cryosphere, into our rising and warming ocean. Chapter 2 assesses High Mountain areas outside of the polar regions, where glaciers, snow and/or permafrost are common. Chapter 3 moves to the Polar Regions of the northern and southern high latitudes, which are characterised by vast stores of frozen water in ice sheets, glaciers, ice shelves, sea ice and permafrost, and by the interaction of these cryosphere elements and the polar oceans. Chapter 4 examines Sea Level Rise and the hazards this brings to Low-Lying Regions, Coasts and Communities. Chapter 5 focuses on the Changing Ocean, with a particular focus on how climate change impacts on the ocean are altering Marine Ecosystems and affecting Dependent Communities. Chapter 6 is dedicated to assessing Extremes and Abrupt Events, and reflects the potential for rapid and possibly irreversible changes in Earth’s ocean and cryosphere, and the challenges this brings to Managing Risk. The multitude ways in which Low-Lying Islands and Coasts are exposed and vulnerable to the impacts of ocean and cryosphere change, along with resilience and adaptation strategies, opportunities and governance options specific to these settings, is highlighted in integrative CrossChapter Box 9. Subject to Copyedit 1-45 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere This report does not attempt to assess all aspects of the ocean and cryosphere in a changing climate. Examples of research themes that will be covered elsewhere in the IPCC Sixth Assessment Cycle and not SROCC include: assessments of ocean and cryosphere changes in the Sixth Coupled Model Intercomparison Project (CMIP6) experiments (AR6); cryosphere changes outside of polar and high mountain regions (e.g., snow cover in temperate and low altitude settings; AR6); and a thorough assessment of mitigation options for reducing climate change impacts (SR1.5, AR6 WGIII). Each chapter of SROCC presents an integrated storyline on the ocean and/or cryosphere in a changing climate. The chapter assessments each present evidence of the pervasive changes that are already underway in the ocean and cryosphere (Figure 1.5). The impacts that physical changes in the ocean and cryosphere have had on ecosystems and people are assessed, along with lessons learned from adaptation measures that have already been employed to avoid adverse impacts. The assessments of future change in the ocean and cryosphere demonstrate the growing and accelerating changes projected for the future, and identify the reduced impacts and risks that choices for a low greenhouse gas emission future would have compared with a high emission future (Figure 1.5). Potential adaptation strategies to reduce future risks to ecosystems and people are assessed, including identifying where limits to adaptation may be exceeded. The local to global scale responses for charting climate-resilient development pathways are also assessed. Subject to Copyedit 1-46 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere Figure 1.5: Changes in the ocean and cryosphere that have already occurred, and projected future changes this century under low (RCP2.6) and high (RCP8.5) greenhouse gas emission scenarios. Context is shown by changes in: (a) atmospheric carbon dioxide concentration {Cross-Chapter Box 1 in Chapter 1, Figure 1.3}; and (b) global population including the range of future population scenarios for global, high mountain and low-elevation coastal populations across the Shared Socioeconomic Pathways. Additionally, around 4 million people live in the Arctic (2010), with an increase of 4% projected for 2030 {1.1, 2.1, 4.3, CrossChapter Box 1 in Chapter 1}. Pervasive and intensifying ocean and cryosphere changes are shown in lower panels for observed (green) and/or modelled historical (brown) changes, and contrasting differences in future changes under high (red; RCP8.5) and low (blue; RCP2.6) greenhouse gas emission scenarios. Changes are shown for: (c) global mean surface air temperature change relative to 1986-2005 with likely range. AR5 assessed that observed surface temperature increase from preindustrial (1850-1900) to 1986-2005 was 0.61 (± 0.6) oC {Cross-Chapter Box 1 in Chapter 1}; (d) Global mean sea level change (metres) relative to 19862005 with likely range {4.2.3}; (e, f) Greenland and Antarctic ice sheet mass loss, as contribution to global sea level (metres), relative to 1992 with ± 1 standard deviation range {3.3.1}; (g) Glacier mass loss, as Subject to Copyedit 1-47 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere contribution to global sea level (metres), relative to 2015 with likely range {Cross-Chapter Box 6 in Chapter 2, Table 4.1}; (h) Global ocean heat content change (0-2000 m depth; in 1021 joules) relative to 1986-2005 with 5-95% range {Figure 5.1}; (i) Global mean sea surface temperature change (°C) relative to 1986-2005 with 5-95% range. {Box 5.1, 5.2.2}; (j) Probability ratio of surface ocean marine heatwaves, global mean relative to 1850-1900 with 5-95% range. A probability ratio of 10 equals a 10-times increase in the probability of experiencing a marine heatwave relative to 1850-1900 {6.4.1}; (k) Global mean surface pH (on the total scale) with 5-95% range. Assessed observational trends between 1980-2012 are centred on 1996 and compiled from open ocean time series site longer than 15 years {Box 5.1, Figure 5.6, 5.2.2}; (l) Arctic sea ice extent in September (millions of km2) with likely range. Observed shading denotes 5-95% range across three satellite-derived products {3.2.1, 3.2.2 Figure 3.3} (Note: Antarctic sea ice is not shown here due to low confidence in future projections {3.2.1); (m) Arctic snow cover in June (land areas north of 60oN in millions of km2) plotted as 5-year moving averages with likely range. Observed shading denotes 5-95% range across 5 snow products {3.4.1, 3.4.2, Figure 3.11}; (n) Near-surface permafrost extent (millions of km2) with likely range {3.4.1, 3.4.2, Figure 3.10}. Differing baseline intervals and temporal coverage of observations reflect data limitations for quantifying the full extent of ocean and cryosphere change since the preindustrial {1.8.1, Figure 1.3}. [START FAQ1.1 HERE] FAQ 1.1: How do changes in the ocean and cryosphere affect our life on planet Earth? The ocean and cryosphere regulate the climate and weather on Earth, provide food and water, support economies, trade and transportation, shape cultures and influence our well-being. Many of the recent changes in Earth’s ocean and cryosphere are the result of human activities and have consequences on everyone’s life. Deep cuts in greenhouse gas emissions will reduce negative impacts on billions of people and help them adapt to changes in their environment. Improving education and combining scientific knowledge with Indigenous knowledge and local knowledge helps communities to further address the challenges ahead. The ocean and cryosphere—a collective name for the frozen parts of the Earth—are essential to the climate and life-giving processes on our planet. Changes in the ocean and cryosphere occur naturally, but the speed, magnitude, and pervasiveness of the global changes happening right now have not been observed for millennia or longer. Evidence shows that the majority of ocean and cryosphere changes observed in the past few decades are the result of human influences on Earth’s climate. Every one of us benefits from the role of the ocean and cryosphere in regulating climate and weather. The ocean has absorbed about a third of the carbon dioxide humans have emitted from the burning of fossil fuels since the Industrial Revolution, and the majority (more than 90%) of the extra heat within the Earth system. In this way, the ocean has slowed the warming humans and ecosystems have experienced on land. The reflective surface of snow and ice reduce the amount of the sun’s energy that is absorbed on Earth. This effect diminishes as snow and ice melts, contributing to amplified temperature rise across the Arctic. The ocean and cryosphere also sustain life-giving water resources, by rain and snow that come from the ocean, and by meltwater from snow and glaciers in mountain and polar regions. Nearly two billion people live near the coast, and around 800 million on land less than 10 m above sea level. The ocean directly supports the food, economies, cultures and well-being of coastal populations (see FAQ 1.2). The livelihoods of many more are tied closely to the ocean through food, trade, and transportation. Fish and shellfish contribute about 17% of the non-grain protein in human diets, and shipping transports at least 80% of international imports and exports. But the ocean also brings hazards to coastal populations and infrastructure, and particularly to low-lying coasts. These populations are increasingly exposed to tropical cyclones, marine heat waves, sea level rise, coastal flooding and saltwater incursion into groundwater resources. Subject to Copyedit 1-48 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere In high mountains and the Arctic, around 700 million people live in close contact with the cryosphere. These people, including many Indigenous Peoples, depend on snow, glaciers and sea ice for their livelihoods, food and water security, travel and transport, and cultures (see FAQ 1.2). They are also exposed to hazards as the cryosphere changes, including flood outbursts, landslides and coastal erosion. Changes in the polar and high mountain regions also have far-reaching consequences for people in other parts of the world (see FAQ 3.1). Warming of the climate system leads to sea level rise. Melt from glaciers and ice sheets is adding to the amount of water in the ocean, and the heat being absorbed by the ocean is causing it to expand and take up more space. Today’s sea level is already about 20 cm higher than in 1900. Sea level will continue to rise for centuries to millennia because the ocean system reacts slowly. Even if global warming were to be halted, it would take centuries or more to halt ice sheet melt and ocean warming. Enhanced warming in the Arctic and in high mountains is causing rapid surface melt of glaciers and the Greenland ice sheet. Thawing of permafrost is destabilising soils, human infrastructure, and Arctic coasts, and has the potential to release vast quantities of methane and carbon dioxide into the atmosphere that will further exacerbate climate change. Widespread loss of sea ice in the Arctic is opening up new routes for shipping, but at the same time is reducing habitats for key species and affecting the livelihoods of Indigenous cultures. In Antarctica, glacier and ice sheet loss is occurring particularly quickly in places where ice is in direct contact with warm ocean water, further contributing to sea level rise. Ocean ecosystems are threatened globally by three major climate change-induced stressors: warming, loss of oxygen, and acidification. Marine heat waves are occurring everywhere across the surface ocean, and are becoming more frequent and more intense as the ocean warms. These are causing disease and mass-mortality that put, for example, coral reefs and fish populations at risk. Marine heat waves last much longer than the heat waves experienced on land, and are particularly harmful for organisms that cannot move away from areas of warm water. Warming of the ocean reduces not only the amount of oxygen it can hold, but also tend to stratify it. As a result, less oxygen is transported to depth, where it is needed to support ocean life. Dissolved carbon dioxide that has been taken up by the ocean reacts with water molecules to increase the acidity of seawater. This makes the water more corrosive for marine organisms that build their shells and structures out of mineral carbonates, such as corals, shellfish and plankton. These climate-change stressors occur alongside other human-driven impacts, such as overfishing, excessive nutrient loads (eutrophication), and plastic pollution. If human impacts on the ocean continue unabated, declines in ocean health and services are projected to cost the global economy $428 billion per year by 2050, and $1.979 trillion per year by 2100. The speed and intensity of the future risks and impacts from ocean and cryosphere change depend critically on future greenhouse gas emissions. The more these emissions can be curbed, the more the changes in the ocean and cryosphere can be slowed and limited, reducing future risks and impacts. But humankind is also exposed to the effects of changes triggered by past emissions, including sea level rise that will continue for centuries to come. Improving education and using scientific knowledge alongside local knowledge and Indigenous knowledge can support the development of context-specific options that help communities to adapt to inevitable changes and respond to challenges ahead. [END FAQ1.1 HERE] [START FAQ1.2 HERE] FAQ 1.2: How will changes in the ocean and cryosphere affect meeting the Sustainable Development Goals? Ocean and cryosphere change affect our ability to meet the United Nations Sustainable Development Goals (SDGs). Progress on the SDGs support climate action that will reduce future ocean and cryosphere change, and as well as the adaptation responses to unavoidable changes. There are also trade-offs between SDGs and Subject to Copyedit 1-49 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere measures that help communities to adjust to their changing environment, but limiting greenhouse gas emissions opens more options for effective adaptation and sustainable development. The Sustainable Development Goals (SDGs) were adopted by the United Nations in 2015 to support action for people, planet, and prosperity (FAQ 1.2, Figure 1). The 17 goals, and their 169 targets, strive to end poverty and hunger, protect the planet, and reduce gender, social, and economic inequities by 2030. SDG 13 (Climate Action) explicitly recognises that changing climatic conditions are a global concern. Climate change is already causing pervasive changes in Earth’s ocean and cryosphere (FAQ 1.1). These changes are impacting food, water, and health securities, with consequences for achieving SDG 2 (Zero Hunger), SDG 3 (Good Health and Well-Being), SDG 6 (Clean Water and Sanitation), and SDG 1 (No Poverty). Climate change impacts on Earth’s ocean and cryosphere also affect the environmental goals for SDG 14 (Life below Water) and SDG 15 (Life on Land), with additional implications for many of the other SDGs. SDG 6 (Clean Water and Sanitation) will be affected by ocean and cryosphere changes. Melting mountain glaciers bring an initial increase in water, but as glaciers continue to shrink so too will the essential water they provide to millions of mountain dwellers, downstream communities, and cities. These populations also depend on water flow from the high mountains for drinking, sanitation, and irrigation, and for SDG 7 (Affordable and Clean Energy). Water security is also threatened by changes in the magnitude and seasonality of rainfall, driven by rising ocean temperatures, which increases the risk of severe storms and flooding in some regions, or the risk of more severe or more frequent droughts in other regions. Among other effects, ongoing sea level rise is allowing salt water to intrude further inland, contaminating drinking water and irrigation sources for some coastal populations. Actions to address these threats will likely require new infrastructure to manage rain, melt-water, and river flow, in order to make water supplies more reliable. These actions would also benefit SDG 3 (Good Health and Well-Being) by reducing the risk of flooding and negative health outcomes posed by extreme rainfall and outbursts of glacial melt. Climate change impacts on the ocean and cryosphere also have many implications for progress on food security that is addressed in SDG 2 (Zero Hunger). Changes in rainfall patterns caused by ocean warming will increase aridity in some areas and bring more (or more intense) rainfall to others. In mountain regions, these changes bring varying challenges for maintaining reliable crops and livestock production. Some adaptation opportunities might be found in developing strains of crops and livestock better adapted to the future climate conditions, but this response option is also challenged by the rapid rate of climate change. In the Arctic, very rapidly warming temperatures, diminishing sea ice, reduced snow cover, and degradation of permafrost are restricting the habitats and migration patterns of important food sources (SDG 2 Zero Hunger), including reindeer and several marine mammals (SDG 15 Life on Land; SDG 14 Life below Water), resulting in reduced hunting opportunities for staple foods that many northern Indigenous communities depend upon. Rising temperatures, and changes in ocean nutrients, acidity, and salinity are altering SDG 14 (Life Below Water). The productivity and distributions of some fish species are changing in ways that alter availability of fish to long-established fisheries, whereas the range of fish populations may move to become available in some new coastal and open ocean areas. Ocean changes are of concern for small island developing states and coastal cities and communities. Beyond possible reductions in marine food supply and related risks for SDG 2 (Zero Hunger), their lives, livelihoods, and well-being are also threatened in ways that are linked to several SDGs, including SDG 3 (Good Health and Wellbeing), SDG 8 (Decent Work and Economic Growth), SDG 9 (Industry, Innovation, and Infrastructure), and SDG 11 (Sustainable Cities and Communities). For example, sea level rise and warming oceans can cause inundation of coastal homes and infrastructure, more powerful tropical storms, declines in established economies such as tourism, and losses of cultural heritage and identity. Improved community and coastal infrastructure can help to adapt to these changes, and more effective and faster disaster responses Subject to Copyedit 1-50 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere from health sectors and other emergency services can assist the populations who experience these impacts. In some situations the most appropriate responses may involve relocation of critical services and, in some cases, communities; and for some populations, migration away from their homeland may become the only viable response. Without transformative adaptation and mitigation, climate change could undermine progress towards achieving the 2030 Sustainable Development Goals, and make it more difficult to implement climateresilient development pathways in the longer term. Reducing global warming (mitigation) provides the best possibility to limit the speed and extent of ocean and cryosphere change and give more options for effective adaptation and sustainable development. Progress on SDG 4 (Quality Education), SDG 5 (Gender Equality) and SDG 10 (Reduced Inequalities) can moderate the vulnerabilities that shape people’s risk to ocean and cryosphere change, while SDG 12 (Responsible Consumption and Production), SDG 16 (Peace, Justice and Institutions) and SDG 17 (Partnerships for the Goals) will help to facilitate the scales of adaptation and mitigation responses required to achieve sustainable development. Investment in social and physical infrastructure that supports adaptation to inevitable ocean and cryosphere changes will enable people to participate in initiatives to achieve the SDGs. Current and past IPCC efforts have focused on identifying ‘climate-resilient development pathways.’ Such adaptation and mitigation strategies, supported by adequate investments, and understanding the potential for SDG initiatives to increase the exposure or vulnerability of the activities to climate change hazards, could also constitute pathways for progress on the Sustainable Development Goals. Subject to Copyedit 1-51 Total pages: 72 FINAL DRAFT Chapter 1 IPCC SR Ocean and Cryosphere FAQ 1.2, Figure 1: The United Nations 2030 Sustainable Development Goals [END FAQ1.2 HERE] Acknowledgements Thanks are due to Mohd Abdul Fahad, Mohamed Khamla, Jelto von Schuckmann and Debabrat Sukla for their assistance with early versions of figures and graphics. 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Subject to Copyedit 1-72 Total pages: 72 FINAL DRAFT Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere Chapter 1: Framing and Context of the Report Supplementary Material Coordinating Lead Authors: Nerilie Abram (Australia), Jean-Pierre Gattuso (France), Anjal Prakash (Nepal/India) Lead Authors: Lijing Cheng (China), Maria Paz Chidichimo (Argentina), Susan Crate (USA), Hiroyuki Enomoto (Japan), Matthias Garschagen (Germany), Nicolas Gruber (Switzerland), Sherilee Harper (Canada), Elisabeth Holland (Fiji), Raphael Martin Kudela (USA), Jake Rice (Canada), Konrad Steffen (Switzerland), Karina von Schuckmann (France) Contributing Authors: Nathaniel Bindoff (Australia), Sinead Collins (UK), Rebecca Colvin (Australia), Daniel Farinotti (Switzerland), Nathalie Hilmi (France/Monaco), Jochen Hinkel (Switzerland), Regine Hock (USA), Alexandre Magnan (France), Michael Meredith (UK), Avash Pandey (Nepal), Mandira Singh Shrestha (Nepal), Anna Sinisalo (Nepal/Finland), Catherine Sutherland (South Africa), Phillip Williamson (UK) Review Editors: Monika Rhein (Germany), David Schoeman (Australia) Chapter Scientists: Avash Pandey (Nepal), Bethany Ellis (Australia) Date of Draft: 14 June 2019 Notes: TSU Compiled Version Table of Contents SM1.1 Supplementary Material Supporting the Text in Section 1.4. ....................................................... 2 SM1.2 Supplementary Material Supporting the Text in Cross-Chapter Box 1 in Chapter 1 ................ 7 SM1.3 Supplementary Material Supporting Figure 1.2 .......................................................................... 11 SM1.4 Supplementary Material for Figure 1.3......................................................................................... 11 References ...................................................................................................................................................... 14 Do Not Cite, Quote or Distribute SM1-1 Total pages: 15 FINAL DRAFT SM1.1 Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere Supplementary Material Supporting the Text in Section 1.4. Table SM1.1. Development of assessments of climate, ocean and cryosphere change across past IPCC working group 1 assessment reports. This table supports the text in Section 1.4. The material is derived from the Summary for Policy Makers (SPM) sections of the Working Group I reports of the First Assessment Report (IPCC, 1990) the Second Assessment Report (IPCC, 1995), the Third Assessment Report (IPCC, 2001) , the Fourth Assessment Report (IPCC, 2007) and the Fifth Assessment Report (IPCC, 2013). Report Global context Cryosphere First Assessment Global mean surface temperature has Report SPM (1990): increased by 0.3°C to 0.6°C over the observed change last 100 years. The unequivocal detection of the enhanced greenhouse effect from observations is not likely for a decade or more. Retreat of most mountain glaciers since the end of the nineteenth century. First Assessment Likely increase in global mean Report SPM (1990): temperature of about 3°C above the projected changea present (about 4°C above preindustrial) before the end of the next century, under a business-as-usual scenario. The West Antarctic ice sheet is of special concern. Within the next century it is not likely that there will be a major outflow of ice from West Antarctica due directly to global warming. Ocean Global sea level has increased by 0.1 to 0.2 m [over the last 100 years]. Key areas of scientific uncertainty [include] the exchange of energy between the oceans and the atmosphere, between the upper layers of the ocean and the deep ocean, and transport within the ocean. Second Assessment Global mean surface air temperature Report SPM (1995): has increased by between about 0.3 observed change and 0.6°C since the late 19th Century. The balance of evidence suggests a discernible human influence on global climate. Second Assessment The lowest emission scenario with a Report SPM (1995): low value of climate sensitivity leads projected changeb to a projected temperature increase of about 1°C by 2100. The highest emission scenario with a high value of climate sensitivity gives warming of about 3.5°C [by 2100, relative to 1990]. Do Not Cite, Quote or Distribute Sea level Predicted rise is about 0.2 m in global mean sea level by 2030, and 0.65 m by the end of the next century. Over the next 100 years the effect of the Antarctic and Greenland ice sheets is expected to be small. Grounds for believing that future warming will lead to an acceleration in sea level rise. Global sea level has risen by between 0.1 and 0.25 m over the past 100 years and much of the rise may be related to the increase in global mean temperature. Models project that between one-third Most simulations show a reduction in and one-half of existing mountain the strength of the north Atlantic glacier mass could disappear over the thermohaline circulation [AMOC]. next 100 years. Little change in the extent of the Greenland and Antarctic ice sheets is expected over the next 50-100 years. SM1-2 Total pages: 15 The lowest emission scenario with low climate and ice-melt sensitivities gives a projected sea level rise of about 0.15 m from the present to 2100. The highest emission scenario combined with high climate and ice-melt sensitivities gives a sea level rise of about 0.95m from present to 2100. FINAL DRAFT Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere Third Assessment The global average surface Report SPM (2001): temperature has increased over the observed change 20th century by about 0.6°C (± 0.2°C). There is new and stronger evidence that most of the warming observed over the last 50 years is attributed to human activities. Snow cover and ice extent have decreased. There are very likely to have been decreases of about 10% in the extent of snow cover since the late 1960s. Third Assessment Global average temperature and sea Report SPM (2001): level are projected to rise under all projected change3 IPCC SRES scenarios. The globally average surface temperature is projected to increase by 1.4 to 5.8°C over the period 1990-2100. Northern Hemisphere snow cover and Most models show weakening of the Global mean sea level is projected to sea-ice extent are projected to decrease ocean thermohaline circulation, but do rise by 0.09 to 0.88 m between 1990 further. not exhibit complete shut-down of the and 2100. thermohaline circulation by 2100. Glaciers and ice caps are projected to Beyond 2100 the thermohaline continue their widespread retreat circulation could completely, and during the 21st century. The Greenland possibly irreversibly, shut down in ice sheet is likely to lose mass. The either hemisphere. Antarctic ice sheet is likely to gain mass because of greater precipitation. Increases in tropical cyclone peak Concerns have been expressed about wind intensities and in mean and peak the stability of the West Antarctic ice precipitation intensities are likely over sheet, however loss of grounded ice some areas. leading to substantial sea level rise from this source is now widely agreed to be very unlikely during the 21st century. Do Not Cite, Quote or Distribute Global average sea level rose between 0.1 and 0.2 m during the 20th century. It is very likely that the 20th century Warm episodes of the El Ninowarming has contributed significantly Southern Oscillation (ENSO) to the observed sea level rise, through phenomenon have been more frequent, thermal expansion of sea water and There has been a widespread retreat of persistent and intense since the midwidespread loss of land ice. Within mountain glaciers in non-polar regions 1970s compared with the previous 100 present uncertainties, observations and during the 20th century. Northern years. models are both consistent with a lack Hemisphere spring and summer seaof significant acceleration of sea level ice extent has decreased by about 10 to rise during the 20th century. 15% since the 1950s. SM1-3 Global ocean heat content has increased since the last 1950s. Total pages: 15 FINAL DRAFT Chapter 1 Supplementary Material Fourth Assessment Warming of the climate system is Report SPM (2007): unequivocal, as is now evident from observed change observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level. Temperature increase from 1850-1899 to 2001-2005 is 0.76 [0.57 to 0.95] °C. Arctic temperatures increased at almost twice the global average rate in the past 100 years. IPCC SR Ocean and Cryosphere Mountain glaciers and snow cover have declined on average in both hemispheres. Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80% of the heat added to the climate system. Total 20th century global mean sea level rise is estimated to be 0.17 [0.12 to 0.22] m. There is high confidence that the rate of observed sea level rise Temperatures at the top of the increased from the 19th to the 20th permafrost layer have generally Century. It is very likely that increases since the 1980s in the Arctic. anthropogenic activity contributed to a Seasonally frozen ground has There is observational evidence for an rise in average sea level. There has decreased by around 7% in the increase of intense tropical cyclone likely been an increased incidence of Northern Hemisphere since 1900, with activity in the North Atlantic since extreme high sea level. a decrease in spring of up to 15%. about 1970 (likely), [but] there is no clear trend in the numbers of tropical Data since 1978 show that annual cyclones. average Arctic sea ice extent has shrunk by 2.7 [2.1 to 3.3]% per decade, with larger decreases in summer of 7.4 [5.0 to 9.8]% per decade. New data show that losses from the ice sheets of Greenland and Antarctic have very likely contributed to sea level rise over 1993 to 2003. Fourth Assessment Best estimates and likely ranges for Report SPM (2007): globally average surface air warming projected changec at the end of the 21st Century (20902099, relative to 1980-1999) for the low scenario is 1.8 [1.1 to 2.9]°C and for the high scenario is 4.0 [2.4 to 6.4]°C. Since IPCCs first report in 1990, assessed projections have suggested global averaged temperature increases between about 0.15 and 0.3°C per decade for 1990 to 2005. This can now be compared with observed values of about 0.2°C per decade, strengthening confidence in near-term projections. Do Not Cite, Quote or Distribute Snow cover is projected to contract. Widespread increases in thaw depth are projected over most permafrost regions. Sea ice is projected to shrink in both the Arctic and Antarctic under all SRES scenarios. In some projections, Arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century. Contraction of the Greenland ice sheet is projected to continue to contribute to sea level rise after 2100. Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming. SM1-4 Projections give reductions in average global surface ocean pH of between 0.14 and 0.35 units over the 21st century, adding to the present decrease of 0.1 units since pre-industrial times. It is likely that future tropical cyclones will become more intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of tropical SST. It is very likely that the Atlantic meridional overturning circulation [AMOC] will slow down during the 21st century. It is very unlikely that the AMOC will undergo a large abrupt transition during the 21st century. Longer-term changes in AMOC cannot be assessed Total pages: 15 Model-based likely ranges for globally mean sea level rise at the end of the 21st Century (2090-2099, relative to 1980-1999) for the low scenario are 0.18 to 0.38 m and for the high scenario are 0.26 to 0.59 m. Models used to date do not include the full effects of changes in ice sheet flow. FINAL DRAFT Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere with confidence. Fifth Assessment Warming of the climate system is Report SPM (2013): unequivocal, and since the 1950s, observed change many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased. The total increase [in global mean surface temperature] between the average of the 1850-1900 period and the 20032012 period is 0.78 [0.72 to 0.85] °C. Do Not Cite, Quote or Distribute Over the last two decades the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent, and permafrost temperatures have increased in most regions (high confidence). See IPCC 2013 (AR5 SPM) for extensive quantification of observed cryosphere changes. SM1-5 Ocean warming accounts for more than 90% of the energy accumulated between 1971 and 2010 (high confidence). It is virtually certain that the upper ocean (0-700m) warmed from 1971 to 2010, and it likely warmed between the 1987s and 1971. There is no observational evidence of a trend in the AMOC. The pH of ocean surface water has decreased by 0.1 since the beginning of the industrial era (high confidence), corresponding to a 26% increase in hydrogen ion concentration. Total pages: 15 Over the period 1901 to 2010, global mean sea level rose by 0.19 [0.17 to 0.21] m. The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia. FINAL DRAFT Chapter 1 Supplementary Material Fifth Assessment Increase in global mean surface Report SPM (2013): temperatures for 2081-2100 relative to projected changed 1986-2005 is projected to likely be in the range of 0.3 to 1.7°C for a low emission future (RCP2.6) or 2.6 to 4.8°C for a high emission future (RCP8.5). The observed warming from 1850-1900 (pre-industrial) to 19862005 is 0.61 [0.55 to 0.67]°C. IPCC SR Ocean and Cryosphere Reductions in Arctic sea ice extent projected by the end of the 21st century range from 43% (RCP2.6) to 94% (RCP8.5) in September. A nearly ice-free Arctic Ocean in September before mid-century is likely for RCP8.5. Best estimates of ocean warming in the top 100 m are about 0.6°C (RCP2.6) to 2.0°C (RCP8.5), and about 0.3°C (RCP2.6) to 6°C (RCP8.5) at a depth of about 1000 m by the end of the 21st century. Global mean sea level rise for 20812100 relative to 1986-2005 will likely be in the ranges of 0.26 to 0.55 m for a low emission future (RCP2.6), and 0.45 to 0.82 m for a high emission future (RCP8.5). For RCP8.5, the rise by the year 2100 is 0.52 to 0.98 m, It is very likely that the AMOC will relative to 1986-2005. It is virtually A decrease in Antarctic sea ice extent weaken over the 21st century by 11 [1- certain that global mean sea level rise 24]% in RCP2.6, and 34 [12-54]% in will continue beyond 2100. and volume is projected with low RCP8.5. It is very unlikely that the confidence for the end of the 21st AMOC will undergo an abrupt century. By the end of the 21st transition of collapse in the 21st century: global glacier volume is projected to decrease by 15 to 55% for century, however a collapse beyond the 21st century for large sustained RCP2.6 and by 35-85% for RCP8.5 warming cannot be excluded. (medium confidence), Northern Hemisphere spring snow cover is projected to decrease by 7% for RCP2.6 and 25% in RCP8.5, and the area of permafrost near the surface (upper 3.5m) is projected to decrease by between 37% (RCP2.60 to 81% (RCP8.5). A decrease in surface ocean pH by the end of the 21st century is in the range of 0.06 to 0.07 for RCP2.6 and 0.30 to 0.32 for RCP8.5. Notes: (a) Business-as-usual scenario used in the First Assessment Report report assumes few or no steps are taken to limit greenhouse gas emissions, and has an atmospheric CO2 concentration of around 830 ppm by 2100. (b) Second Assessment Report uses the IS92 emission scenarios. The lowest emission scenario is IS92c, and the highest emission scenario is IS92e. (c) The Third and Fourth Assessment Reports use the SRES emission scenarios, which have a range of atmospheric carbon dioxide concentrations at 2100 of between 540 to 970 ppm (see SM1.2). (d) AR5 uses the RCP emission scenarios (Cross-Chapter Box 1 in Chapter 1; SM1.2). Do Not Cite, Quote or Distribute SM1-6 Total pages: 15 FINAL DRAFT SM1.2 Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere Supplementary Material Supporting the Text in Cross-Chapter Box 1 in Chapter 1 Additional details are provided below on the Representative Concentration Pathways (RCPs), the Shared Socio-economic Pathways (SSPs) and the Special Report on Emission Scenarios (SRES), supporting the Cross-Chapter Box 1 in Chapter 1. Five SSP narratives describe alternative pathways for future society (Figure SM1.1). Each SSP looks at how the different RCPs could be achieved within the context of the underlying socioeconomic characteristics and shared policy assumptions of that world. The SSPs five alternative socio-economic futures compromise: sustainable development (SSP1), middle-of-the-road development (SSP2), regional rivalry (SSP3), inequality (SSP4), and fossil-fuelled development (SSP5) (Kriegler et al., 2016; Riahi et al., 2017). Across these five SSP narratives there are a total of 23 ‘Marker’ SSP scenarios. Appendix 1.A, Figure 2 shows some specific SSP Markers compared with the RCPs, according to (O'Neill et al., 2016). SSP5-8.5 represents the high end of the range of future pathways, corresponding to RCP8.5. SSP3-7.0 lies between RCP6.0 and RCP8.5, and represents the medium to high end of the range of future forcing pathways. SSP4-6.0 corresponds to RCP6.0, fills in the range of medium forcing pathways. SSP2-4.5 represents the medium part of the range of future forcing pathways and updates RCP4.5. SSP5-3.4 (Overshoot) fills a gap in existing climate simulations by investigating the implications of a substantial 21st century overshoot in radiative forcing relative to a longer-term target. SSP4-3.4 fills in the range of low forcing pathways, and there is substantial mitigation policy interest in this scenario that reaches 3.4 W m–2 by 2100. SSP1-2.6 is similar to RCP2.6. It is anticipated that it will produce a multi-model mean of less than 2°C warming by 2100. Table CB1.1 provides projections for near-term and end-of-century changes in climate and ocean parameters under different RCP scenarios. Table SM1.2 (below) provides information on the models and ensemble members used for these calculating the data presented in Table CB1.1. Prior to the RCPs, the coupled model intercomparison project used the Special Report on Emission Scenarios (SRES) (Nakicenovic and Swart, 2000; Table SM1.3). SRES includes four qualitative storylines, yielding four sets of scenarios called ‘families’: A1, A2, B1, and B2. The A1 family describes a future world of very rapid economic growth, global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies. The A1 family develops into three groups distinguished by their technological emphasis: fossil-fuel intensive (A1FI), non-fossil energy sources (A1T), or a balance across all sources (A1B). The A2 family describes a very heterogeneous world. The underlying theme is self-reliance and preservation of local identities. The B1 family describes a convergent world with a global population that peaks in mid-century and declines thereafter (as in the A1 storyline), but with rapid changes in economic structures toward a service and information economy, reductions in material intensity, and the introduction of clean and resource-efficient technologies. The B2 family describes a world in which the emphasis is on local solutions to economic, social, and environmental sustainability. With respect to radiative forcing, RCP4.5 is close to SRES B1, RCP6.0 is close to SRES A1B, and RCP8.5 is somewhat higher than A2 and close to the SRES A1FI scenario. RCP2.6 is lower than any of the SRES (Cubasch et al., 2013; Stocker et al., 2013). Table SM1.3 gives SRES projections for global mean surface air temperature for the near-term and end-of-century, and Table SM1.4 gives details of the models used in calculating these projections. Do Not Cite, Quote or Distribute SM1-7 Total pages: 15 FINAL DRAFT Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere Figure SM1.1: Radiative forcing (W m–2) time series for historical data (1765–2004), and for future scenarios from the Representative Concentration Pathways (RCP; 2005–2100) and their continuation as the extended RCPs (2100–2500), and the Shared Socio-economic Pathways (SSP; 2005–2100). The RCP scenarios are shown as dashed curves, and SSPs are shown as solid curves (‘Marker’ scenarios are used). Note the change in x-axis scale for the 2005–2100 interval to give an improved illustration of radiative forcing scenarios during the 21st century. Table SM1.2. List of the CMIP5 GCM model runs used for Table CB1.1. Ensemble members used are “r1i1p1” except otherwise indicated. CMIP5 model name Global mean surface air temperature RCP2.6 RCP4.5 RCP6.0 RCP8.5 ACCESS1-0 X X ACCESS1.3 X X Global mean sea surface temperature Surface pH Dissolved oxygen (100-600 m) RCP2.6 RCP8.5 RCP2.6 RCP8.5 RCP2.6 X X X X bcc-csm1-1 X X X X bcc-csm1-1-m X X X X BNU-ESM X X X CanESM2 X X X X X CCSM4 X X X X X X X CESM1-BGC CESM1-CAM5 X X X X CMCC-CESM X X X X X CMCC-CM X X CMCC-CMS X X Do Not Cite, Quote or Distribute RCP8.5 SM1-8 Total pages: 15 FINAL DRAFT Chapter 1 Supplementary Material CNRM-CM5 X X CSIRO-Mk3-6-0 X X CSIRO-Mk3L-1-2 X X X X IPCC SR Ocean and Cryosphere X r1i2p1 EC-EARTH r8i1p1 X X FGOALS_g2 X X X FIO-ESM X X X X GFDL-CM3 X X X X X X GFDL-ESM2G X X X X X X X X GFDL-ESM2M X X X X X X X X GISS-E2-H X X X X X X X X GISS-E2-H-CC GISS-E2-R X X GISS-E2-R-CC HadGEM2-AO X X X inmcm4 X X X X X X X X X HadGEM2-CC HadGEM2-ES X X X X r2i1p1 X X X IPSL-CM5A-LR X X X X X X X X X X IPSL-CM5A-MR X X X X X X X X X X IPSL-CM5B-LR X X MIROC-ESM X X X X MIROC-ESMCHEM X X X X MIROC5 X X X X MPI-ESM-LR X X X MPI-ESM-MR X X X MRI-CGCM3 X X X MRI-ESM1 X X X X X X X X X X X X X X X X X X NorESM1-M X X X X NorESM1-ME X X X X Do Not Cite, Quote or Distribute SM1-9 Total pages: 15 FINAL DRAFT Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere Table SM1.3. SRES global mean surface air temperature changes, relative to the recent past (1986-2005), and approximate RCP equivalent. AR5 assessed that observed warming from the pre-industrial to the 1986-2005 reference period was 0.61 oC (likely range of 0.55 oC to 0.67 oC). 2031-2050 2080-2099 Approximate RCP equivalent Scenario Mean 5-95% range Mean 5-95% range B1 0.8 oC 0.4 to 1.1 oC 1.6 oC 1.0 to 2.2 oC RCP4.5 A1B 1.1 oC 0.6 to 1.6 oC 2.4 oC 1.7 to 3.2 oC RCP6.0 A2 1.0 oC 0.6 to 1.5 oC 3.0 oC 2.2 to 3.7 oC RCP8.5 Table SM1.4. List of the CMIP3 General Circulation Model runs used for Table SM1.3. Global mean surface air temperature in SRES experiments CMIP5 model name B1 A1B A2 BCCR-BCM2-0 run1 run1 run1 CCCMA-CGCM3-1 run1 run1 run1 CCCMA-CGCM3-1-T63 run1 run1 CNRM-CM3 run1 run1 run1 CSIRO-Mk3-0 run1 run1 run1 GFDL-CM2-0 run1 run1 run1 GFDL-CM2-1 run1 run1 run1 GISS-AOM run1 run1 GISS-MODEL-E-H IAP-FGOALS1-0-G run1 run1 run1 INGV-ECHAM4 run1 run1 inmcm3-0 run1 run1 run1 IPSL-CM4 run1 run1 run1 MIROC3-2-MEDRES run1 run1 run1 MIUB-ECHO-G run1 run1 run1 MPI-ECHAM5 run1 run1 run1 MRI-CGCM2-3-2A run1 run1 run1 NCAR-CCSM3-0 run1 run1 run1 NCAR-PCM1 run2 run2 run1 UKMO-HadCM3 run1 run1 run1 Do Not Cite, Quote or Distribute SM1-10 Total pages: 15 FINAL DRAFT Chapter 1 Supplementary Material UKMO-HadGEM1 SM1.3 IPCC SR Ocean and Cryosphere run1 Supplementary Material Supporting Figure 1.2 Additional details are provided below on the main responses to observed and expected changes in the ocean and cryosphere in a changing climate including mitigation and adaptation measures. These details expand on the summary provided in Figure 1.2. Supporting biological and ecological adaptation (including ecosystem-based management) • Pollution reduction: Reduce pollution from land and rivers and atmosphere • Conservation: Protect habitats and ecosystems through spatial measures including terrestrial and marine protected areas • Assisted evolution: Assisted evolution (active intervention to accelerate the rate of naturally occuring evolutionary processes) and genetic modifications • Restoration and enhancement: of habitats, ecosystems and ecosystem services; ecological engineering; assisted migration Addressing the causes of climate change • Reduce atmospheric pollution, including emissions from shipping and black carbon • Renewable energy: Energy substitution for fossil energy • Increase energy efficiency • Carbon capture and storage: Sequestration of CO2 underground on land and under sea floor • Direct air capture and storage • Bioenergy with carbon capture and storage: Crops are burnt in power plants to generate energy and resulting CO2 is captured and stored • Biochar and soil carbon: Carbon, including from partly burnt biomass added to soil • Afforestation and reforestation: Including blue carbon from marine and coastal vegetation to enhance CO2 uptake and avoid further emissions • Enhance open-ocean productivity by adding nutrients and cultivating marine plants • Enhanced weathering and alkalinization: Addition of natural or man-made alkalinity to enhance CO2 removal and/or carbon storage Enhancing societal adaptation • Community-based adaptation: Enhance local social capital, gender equity, indigenous knowledge, local knowledge... • Infrastructure-based adaptation: Building standards, hard defences... • Relocate and diversify economics activities • Relocate people: Coastal retreat and migration Change practices and policies: Resource use, consumption modes, urban planning, regulation. SM1.4 Supplementary Material for Figure 1.3 The lower panel of Figure 1.3 gives examples of available data/output for the ocean and cryosphere (Section 1.8.1). Heights depict the number of observations, parameters or simulations available through time expressed relative to the maximum data availability, and colour scale depicts spatial coverage of data across the relevant domain. Details and data sources are: • Physical Ocean (temperature and salinity) observations are from the World Ocean Database (Boyer et al., 2013). The data in Figure 1.3 shows the number of observations in the database through time for three depth layers, relative to maximum annual values of 1,102,401 for the 0–800 m layer, 382,619 for the 800–2000 m layer, and 12,875 for observations deeper than 2000 m. Spatial coverage is calculated as the percentage of 3° x 3° ocean grid cells that have observations. Additional detail of the spatial Do Not Cite, Quote or Distribute SM1-11 Total pages: 15 FINAL DRAFT Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere coverage of ocean temperature and salinity observations by depth is given below in Figure SM1.2. Database: https://www.nodc.noaa.gov/OC5/WOD/pr_wod.html Figure SM1.2: Further detail on the spatial coverage of ocean in situ temperature (upper) and salinity (lower) observations from the sea surface to 6000 m depth in the World Ocean Database (Boyer et al., 2013). Coverage is calculated as the percentage of 3° x 3° ocean grid cells that have observations. Coverage calculations at each depth layer take into account the changing lateral extent of the ocean at different depth levels. The figure is adapted and extended based on Rhein et al. (2013) and Meyssignac et al. (2019). • Ocean biogeochemistry (dissolved inorganic carbon; DIC) observations data stem from the Global Ocean Data Analysis Project version 2 (GLODAPv2) product (Olsen et al., 2016), in which the vast majority of all available DIC data since the early 1970s were assembled. It is composed of data from 724 scientific cruises covering the global ocean. The data plotted represent the number of distinct samples measured as a function of time from the surface down to the bottom of the ocean. The bi-modal distribution is a result of the two large survey campaigns that underlie these data, i.e., the JGOFS/WOCE Do Not Cite, Quote or Distribute SM1-12 Total pages: 15 FINAL DRAFT Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere survey in the 1980s and 1990s (Wallace, 2001) and the ongoing Repeat Hydrography/GOSHIP survey after 2000 (Talley et al., 2016). The spatial coverage in any given year is relatively low owing to the decadal survey character of the programs. Along any survey line, the spatial coverage tends to be high, as a full profile is typically taken at every 1° of latitude/longitude. • Ocean biology (Continuous Plankton Recorder) observations are from the Global Alliance of Continuous Plankton Recorder Surveys (GACS), an international collaboration which encompasses the original CPR Survey and twelve other regional CPR Surveys. Data plotted represent the number of processed CPR samples (subset from the total number of archived samples) from 1936 to 2013. Until 1991 surveys only covered the North Atlantic, then extended into the Southern ocean and in 2000 into the North Pacific so that for two decades there has been sampling in both hemispheres and 3 ocean basins (McQuatters-Gollop et al., 2015). For conversion to spatial area, each sample was considered to cover 10 square nautical miles. Data may be requested at: https://www.cprsurvey.org/data/data-requestform/. • Sea level observations are from tide gauge data archived in the Permanent Service for Mean Sea Level (PSMSL) (PSMSL, 2016). There are a total of 1508 tide gauge sites in the PSMSL database and these are located around the world’s coastal and island regions. The maximum number of tide gauges giving measurements in a single year in the PSMSL database is 776. Data coverage is calculated as the percentage of 3° x 3° ocean grid cells that have observations, and the low level (<10%) of ocean coverage is due to tide gauges being located primarily on coasts, rather than across the open ocean. Database: https://www.psmsl.org/data/obtaining/ • Glacier length observations are from the World Glacier Monitoring Service (WGMS, 2017). This database is used as an illustrative example, but other glacier databases include the National Snow and Ice Data Center and the Randolph Glacier Inventory (containing data for 216000 glaciers worldwide). The illustrative data from the WGMS database amalgamate the glacier front variation and glacier reconstructed front variation databases, and show the number of glacier length observations through time relative to a maximum annual value of 837. The percentage coverage is based on the number of glaciers with length observations relative to the total number of glacier identification codes in the WGMS database (8490). Database doi: 10.5904/wgms-fog-2017-10. • Remote sensing (surface ocean) shows the availability through time of systematic and sustained satellite monitoring of six surface ocean parameters: sea surface temperature, sea surface salinity, ocean colour, ocean wind, ocean height and ocean mass change. Remote sensing (cryosphere) shows the availability through time of systematic and sustained satellite monitoring of: sea ice extent, snow cover, glacier and ice sheet area, and glacier and ice sheet mass change (Dowell et al., 2013; Raup et al., 2015) • Palaeoclimate data uses an example from the PAGES2k version 2.0.0 database (PAGES2K Consortium, 2017) of temperature sensitive records, which include temperature proxies over ice sheets (from ice cores) and in the ocean (from corals and marine sediments). Figure 1.3 shows the number of palaeoclimate records available through time, relative to an annual maximum of 649. Spatial coverage is calculated as the percentage of 3° x 3° surface grid cells across the globe that have palaeoclimate data. Database doi: 10.6084/m9.figshare.c.3285353 • Model simulation outputs in Figure 1.3 are based on search results for CMIP5 simulations (Taylor et al., 2012) in the Earth System Grid Federation database (http://esgf.llnl.gov/), using the search criteria of last millennium (p1000; 850–1850 CE), historical (1851–2005 CE), RCP (2005–2100 CE), and RCPextended (2100 CE onwards) experiments with monthly resolution output for the ocean. Data availability is shown relative to the maximum number of datasets meeting these search criteria (508 for RCP experiments). Do Not Cite, Quote or Distribute SM1-13 Total pages: 15 FINAL DRAFT Chapter 1 Supplementary Material IPCC SR Ocean and Cryosphere References Boyer, T. P. et al., 2013: World Ocean Database 2013.[Levitus, S. and A. Mishonov (eds.)]. Silver Spring, MD, NOAA Atlas, 209 pp. Cubasch, U. et al., 2013: Introduction. In: Climate Change 2013: The Physical Science Basis. 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Wiley Blackwell, 123-156. Rhein, M. et al., 2013: Observations: Ocean. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. B. And and P. M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 255-315. Riahi, K. et al., 2017: The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: An overview. Global Environmental Change, 42, 153-168, doi:10.1016/j.gloenvcha.2016.05.009. Stocker, T. F. et al., 2013: Technical summary. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S. K. Allen, J. Boschung, A. Nauels, Y. Xia, V. 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Do Not Cite, Quote or Distribute SM1-15 Total pages: 15 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Chapter 2: High Mountain Areas Coordinating Lead Authors: Regine Hock (USA), Golam Rasul (Nepal) Lead Authors: Carolina Adler (Switzerland/Australia), Bolívar Cáceres (Ecuador), Stephan Gruber (Canada/Germany), Yukiko Hirabayashi (Japan), Miriam Jackson (Norway), Andreas Kääb (Norway), Shichang Kang (China), Stanislav Kutuzov (Russia), Alexander Milner (UK), Ulf Molau (Sweden), Samuel Morin (France), Ben Orlove (USA), Heidi Steltzer (USA) Contributing Authors: Simon Allen (Switzerland), Lukas Arenson (Canada), Soumyadeep Baneerjee (India), Iestyn Barr (UK), Roxana Bórquez (Chile), Lee Brown (UK), Bin Cao (China), Mark Carey (USA), Graham Cogley (Canada), Andreas Fischlin (Switzerland), Alex de Sherbinin (USA), Nicolas Eckert (France), Marten Geertsema (Canada), Marca Hagenstad (USA), Martin Honsberg (Germany), Eran Hood (USA), Matthias Huss (Switzerland), Elizabeth Jimenez Zamora (Bolivia), Sven Kotlarski (Switzerland), Pierre-Marie Lefeuvre (Norway/France), Juan Ignacio López Moreno (Spain), Jessica Lundquist (USA), Graham McDowell (Canada), Scott Mills (USA), Cuicui Mou (China), Santosh Nepal (Nepal), Jeannette Noetzli (Switzerland), Elisa Palazzi (Italy), Nick Pepin (UK), Christian Rixen (Switzerland), Maria Shahgedanova (UK), S. McKenzie Skiles (USA), Christian Vincent (France), Daniel Viviroli (Switzerland), Gesa Weyhenmeyer (Sweden), Pasang Yangjee Sherpa (Nepal/USA), Nora Weyer (Germany), Bert Wouters (Netherlands), Teppei J. Yasunari (Japan), Qinglong You (China), Yangjiang Zhang (China) Review Editors: Georg Kaser (Austria), Aditi Mukherji (Nepal/India) Chapter Scientists: Pierre-Marie Lefeuvre (Norway/France), Santosh Nepal (Nepal) Date of Draft: 14 June 2019 Notes: TSU Compiled Version Table of Contents Executive Summary ................................................................................................................................... 3 2.1 Introduction........................................................................................................................................ 7 2.2 Changes in the Mountain Cryosphere ............................................................................................... 8 2.2.1 Atmospheric Drivers of Changes in the Mountain Cryosphere ................................................... 8 Box 2.1: Does Atmospheric Warming in the Mountains Depend on Elevation ? ................................... 10 2.2.2 Snow Cover ............................................................................................................................. 12 2.2.3 Glaciers .................................................................................................................................. 14 Cross-Chapter Box 6: Glacier Projections in Polar and High-mountain Regions ................................. 17 2.2.4 Permafrost .............................................................................................................................. 19 2.2.5 Lake and River Ice .................................................................................................................. 23 Box 2.2: Local, Regional and Global Climate Feedbacks Involving the Mountain Cryosphere............ 24 2.3 Mountain Social-Ecological Systems: Impacts, Risks and Human Responses ............................... 25 2.3.1 Water Resources ..................................................................................................................... 25 FAQ 2.1: How does glacier shrinkage affect river runoff further downhill? ......................................... 28 Box 2.3: Local Responses to Water Shortage in Northwest India .......................................................... 33 2.3.2 Landslide, Avalanche and Flood Hazards................................................................................ 36 Box 2.4: Challenges to Farmers and Local Population Related to Shrinkages in the Cryosphere: Cordillera Blanca, Peru ................................................................................................................... 44 2.3.3 Ecosystems .............................................................................................................................. 45 2.3.4 Infrastructure and Mining ....................................................................................................... 49 2.3.5 Tourism and Recreation .......................................................................................................... 50 2.3.6 Cultural Values and Human Well-being .................................................................................. 52 2.3.7 Migration, Habitability and Livelihoods .................................................................................. 54 Subject to Copyedit 2-1 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere 2.4 International Policy Frameworks and Pathways to Sustainable Development .............................. 56 2.5 Key Gaps in Knowledge and Prospects ........................................................................................... 57 References ................................................................................................................................................ 59 Appendix 2.A: Additional Information on Global and Regional Glacier Mass Change Estimates for 2006–2015 ......................................................................................................................................... 91 Subject to Copyedit 2-2 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Executive Summary The cryosphere (including, snow, glaciers, permafrost, lake and river ice) is an integral element of highmountain regions, which are home to roughly 10% of the global population. Widespread cryosphere changes affect physical, biological and human systems in the mountains and surrounding lowlands, with impacts evident even in the ocean. Building on the IPCC’s Fifth Assessment Report (AR5), this chapter assesses new evidence on observed recent and projected changes in the mountain cryosphere as well as associated impacts, risks and adaptation measures related to natural and human systems. Impacts in response to climate changes independently of changes in the cryosphere are not assessed in this chapter. Polar mountains are included in Chapter 3, except those in Alaska and adjacent Yukon, Iceland, and Scandinavia, which are included in this chapter. Observations of cryospheric changes, impacts, and adaptation in high mountain areas Observations show general decline in low-elevation snow cover (high confidence1), glaciers (very high confidence) and permafrost (high confidence) due to climate change in recent decades. Snow-cover duration has declined in nearly all regions, especially at lower elevations, on average by 5 days per decade, with a likely2 range from 0 to 10 days per decade. Low elevation snow depth and extent have declined, although year-to-year variation is high. Mass change of glaciers in all mountain regions (excluding the Canadian and Russian Arctic, Svalbard, Greenland and Antarctica) was very likely -490±100 kg m-2 yr-1 (123±24 Gt yr-1) in 2006–2015. Regionally averaged mass budgets were likely most negative (less than -850 kg m-2 yr-1) in the southern Andes, Caucasus and central Europe, and least negative in High Mountain Asia (150±110 kg m-2 yr-1) but variations within regions are strong. Between 3.6 and 5.2 million km2 are underlain by permafrost in the eleven high-mountain regions covered in this chapter corresponding to 27–29% of the global permafrost area (medium confidence). Sparse and unevenly distributed measurements show an increase in permafrost temperature (high confidence), for example, by 0.19±0.05ºC on average for about 28 locations in the European Alps, Scandinavia, Canada, and Asia during the past decade. Other observations reveal decreasing permafrost thickness and loss of ice in the ground. {2.2.2, 2.2.3, 2.2.4} Glacier, snow and permafrost decline has altered the frequency, magnitude and location of most related natural hazards (high confidence). Exposure of people and infrastructure to natural hazards has increased due to growing population, tourism and development (high confidence). Glacier retreat and permafrost thaw have decreased the stability of mountain slopes and the integrity of infrastructure (high confidence). The number and area of glacier lakes has increased in most regions in recent decades (high confidence), but there is only limited evidence that the frequency of glacier lake outburst floods has changed. In some regions, snow avalanches involving wet snow have increased (medium confidence), and rain-onsnow floods have decreased at low elevations in spring and increased at high elevations in winter (medium confidence). The number and extent of wildfires have increased in the Western USA partly due to early snow melt (medium confidence). {2.3.2, 2.3.3} Changes in snow and glaciers have changed the amount and seasonality of runoff in snow-dominated and glacier-fed river basins (very high confidence) with impacts on agriculture (medium confidence). Winter runoff has increased in recent decades due to more precipitation falling as rain (high confidence). In some glacier-fed rivers, summer and annual runoff have increased due to intensified glacier melt, but decreased where glacier melt water has lessened as glacier area shrinks. Decreases were observed especially in regions dominated by small glaciers, such as the European Alps (medium confidence). In some areas, 1 In this Report, the following summary terms are used to describe the available evidence: limited, medium, or robust; and for the degree of agreement: low, medium, or high. A level of confidence is expressed using five qualifiers: very low, low, medium, high, and very high, and typeset in italics, e.g., medium confidence. For a given evidence and agreement statement, different confidence levels can be assigned, but increasing levels of evidence and degrees of agreement are correlated with increasing confidence (see Section 1.9.2 and Figure 1.4 for more details). 2 In this Report, the following terms have been used to indicate the assessed likelihood of an outcome or a result: Virtually certain 99–100% probability, Very likely 90–100%, Likely 66–100%, About as likely as not 33–66%, Unlikely 0–33%, Very unlikely 0–10%, and Exceptionally unlikely 0–1%. Additional terms (Extremely likely: 95– 100%, More likely than not >50–100%, and Extremely unlikely 0–5%) may also be used when appropriate. Assessed likelihood is typeset in italics, e.g., very likely (see Section 1.9.2 and Figure 1.4 for more details). This Report also uses the term ‘likely range’ to indicate that the assessed likelihood of an outcome lies within the 17-83% probability range. Subject to Copyedit 2-3 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere where glacier and snow meltwater has decreased, especially where other climatic drivers or socio-economic stressors are also present, agricultural productivity has declined, e.g., in the Western USA, High Mountain Asia and the tropical Andes (medium confidence). There is limited evidence of impacts on operation and productivity of hydropower facilities resulting from changes in seasonality and both increases and decreases in water input, for example, in Central Europe, Iceland, Western Canada and USA, and low latitude Andes. {2.3.1} Species composition and abundance have markedly changed in high-mountain ecosystems in recent decades (very high confidence), partly due to changes in the cryosphere (high confidence). Habitats for establishment by formerly absent species have opened up or been altered by reduced snow cover (high confidence), retreating glaciers (very high confidence), and thawing of permafrost (medium confidence). Reductions in glacier and snow cover have directly altered the structure of many freshwater communities (high confidence). Reduced snow cover has negatively impacted the reproductive fitness of some snowdependent plant and animal species, including foraging and predator-prey relationships of mammals (high confidence). Upslope migration of individual species, mostly due to warming and to a lesser extent due to cryosphere-related changes, has often increased local species richness (very high confidence). Some coldadapted species, including endemics, in terrestrial and freshwater communities have declined in abundance (high confidence). While the plant productivity has generally increased, the actual impact on provisioning, regulating, and cultural ecosystem services varies greatly (high confidence). {2.3.3} Tourism and recreation activities such as skiing, glacier tourism and mountaineering have been negatively impacted by declining snow cover, glaciers and permafrost (medium confidence). In several regions, worsening route safety has reduced mountaineering opportunities (medium confidence). Variability and decline in natural snow cover have compromised the operation of low-elevation ski resorts (high confidence). Glacier and snow decline have impacted aesthetic, spiritual and other cultural aspects of mountain landscapes (medium confidence), reducing the well-being of people. {2.3.5, 2.3.6} Adaptation in agriculture, tourism and drinking water supply has aimed to reduce the impacts of cryosphere change (medium confidence), though there is limited evidence on their effectiveness owing to a lack of formal evaluations, or technical, financial and institutional barriers to implementation. Artificial snowmaking has generally been effective to sustain ski tourism in some regions (medium confidence). Release and storage of water from reservoirs according to sectoral needs (agriculture, drinking water, ecosystems) has reduced the impact of seasonal variability on runoff (medium confidence). {2.3.1, 2.3.5} Future projections of cryospheric changes, their impacts and risks, and adaptation in high mountain areas Snow cover, glaciers and permafrost are projected to continue to decline in almost all regions throughout the 21st century (high confidence). Compared to 1986–2005, low elevation snow depth will likely decrease by 10–40% for 2031–2050, regardless of Representative Concentration Pathway (RCP) and for 2081–2100, likely by 10–40 % for RCP2.6 and by 50–90% for RCP8.5. Projected glacier mass reductions between 2015 and 2100 are likely 22–44% for RCP2.6 and 37–57% for RCP8.5. In regions dominated by smaller glaciers and relatively little ice cover (e.g., Central Europe, Caucasus, Low Latitudes), glaciers will lose more than 80% of their current mass by 2100 under RCP8.5 (medium confidence). Permafrost thaw and degradation will increase during the 21st century (very high confidence) but quantitative projections are scarce. {2.2.2, 2.2.3, 2.4.4} Most types of natural hazards are projected to change in frequency, magnitude and areas affected as the cryosphere continues to decline (medium confidence). Glacier retreat and permafrost thaw are projected to decrease the stability of mountain slopes, and increase the number and area of glacier lakes (medium confidence). Resulting landslides and floods, and cascading events, will also emerge where there is no record of previous events (medium confidence). Snow avalanches are projected to decline in number and runout distance at lower elevation, and avalanches involving wet snow even in winter will occur more frequently (medium confidence). Rain-on-snow floods will occur earlier in spring and later in autumn, and be more frequent at higher elevations and less frequent at lower elevations (high confidence). {2.3.2, 2.3.3} Subject to Copyedit 2-4 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere River runoff in snow-dominated and glacier-fed river basins will change further in amount and seasonality in response to projected snow cover and glacier decline (very high confidence) with negative impacts on agriculture, hydropower and water quality in some regions (medium confidence). The average winter snow melt runoff is projected to increase (high confidence), and spring peaks to occur earlier (very high confidence). Projected trends in annual runoff vary substantially among regions, and can even be opposite in direction, but there is high confidence that in most regions average annual runoff from glaciers will have reached a peak that will be followed by declining runoff at the latest by the end of the 21st century. Declining runoff is expected to reduce the productivity of irrigated agriculture in some regions (medium confidence). Hydropower operations will increasingly be impacted by altered amount and seasonality of water supply from snow and glacier melt (high confidence). The release of heavy metals, particularly mercury, and other legacy contaminants currently stored in glaciers and permafrost, is projected to reduce water quality for freshwater biota, household use and irrigation (medium confidence). {2.3.1} Current trends in cryosphere-related changes in high-mountain ecosystems are expected to continue and impacts to intensify (very high confidence). While high mountains will provide new and greater habitat area, including refugia for lowland species, both range expansion and shrinkage are projected, and at high elevations this will lead to population declines (high confidence). The latter increases the risk of local extinctions, in particular for freshwater cold-adapted species (medium confidence). Without genetic plasticity and/or behavioral shifts, cryospheric changes will continue to negatively impact endemic and native species, such as some coldwater fish (e.g. trout) and species whose traits directly depend on snow (e.g. snowshoe hares) or many large mammals (medium confidence). The survival of such species will depend on appropriate conservation and adaptation measures (medium confidence). Many projected ecological changes will alter ecosystem services (high confidence), affecting disturbance regimes (e.g. fire, rock fall, slope erosion) with considerable impacts on people (medium confidence). {2.3.3} Cultural assets, such as snow- and ice-covered peaks in many UNESCO World Heritage sites, and tourism and recreation activities, are expected to be negatively affected by future cryospheric change in many regions (high confidence). Current adaptation strategies, such as snowmaking to support ski tourism, are projected to be less effective in most parts of Europe, North America and Japan already at 1.5°C global warming relative to the pre-industrial period, with effectiveness further reduced beyond 2°C warming (high confidence). Diversification through year-round activities supports adaptation of tourism under future climate change (medium confidence). {2.3.5, 2.3.6} Enablers and response options to promote adaptation and sustainable development in high mountain areas The already committed and unavoidable climate change affecting all cryosphere elements, irrespective of the emission scenario, point to integrated adaptation planning to support and enhance water availability, access, and management (medium confidence). Integrated management approaches for water, in particular for energy, agriculture, ecosystems and drinking water supply, can be effective at dealing with impacts from changes in the cryosphere. These approaches also offer opportunities to support socialecological systems, through the development and optimization of storage and the release of water from reservoirs (medium confidence), while being cognisant of potential negative implications for some ecosystems. Success in implementing such management options depends on the participation of relevant stakeholders, including affected communities, diverse knowledge and adequate tools for monitoring and projecting future conditions, and financial and institutional resources to support planning and implementation (medium confidence). {2.3.1, 2.3.3, 2.4} Effective governance is a key enabler for reducing disaster risk, considering relevant exposure factors such as planning, zoning, and urbanization pressures, as well as vulnerability factors such as poverty, which can challenge efforts towards resilience and sustainable development for communities (medium confidence). Reducing losses to disasters depend on integrated and coordinated approaches to account for the hazards concerned, the degree of exposure, and existing vulnerabilities. Diverse knowledge that includes community and multi-stakeholder experience with past impacts complements scientific knowledge to anticipate future risks. {CCB-1, 2.3.2, Figure 2.8, Box 2.4, 2.4} Subject to Copyedit 2-5 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere International cooperation, treaties and conventions exist for some mountain regions and transboundary river basins with potential to support adaptation action. However, there is limited evidence on the extent to which impacts and losses arising from changes in the cryosphere are specifically monitored and addressed in these frameworks. A wide range of institutional arrangements and practices have emerged over the past three decades that respond to a shared global mountain agenda and specific regional priorities. There is potential to strengthen them to also respond to climate-related cryosphere risks and open opportunities for development through adaptation (limited evidence, high agreement). The Sustainable Development Goals (SDGs), Sendai Framework and Paris Agreement have directed some attention in mountain-specific research and practice towards the monitoring and reporting on targets and indicators specified therein. {2.3.1, 2.4} Subject to Copyedit 2-6 Total pages: 94 FINAL DRAFT 2.1 Chapter 2 IPCC SR Ocean and Cryosphere Introduction High-mountain regions share common features, including rugged terrain, a low-temperature climate regime, steep slopes and institutional and spatial remoteness. These features are often linked to physical and socialecological processes that, although not unique to mountain regions, typify many of the special aspects of these regions. Due to their higher elevation compared with the surrounding landscape, mountains often feature cryosphere components, such as glaciers, snow cover and permafrost, with a significant influence on surrounding lowland areas even far from the mountains (Huggel et al., 2015a). Hence the mountain cryosphere plays a major role in large parts of the world. Considering the close relationship between mountains and the cryosphere, high mountain areas are addressed in a dedicated chapter within this special report. Almost 10% (671 million people) of the global population lived in high-mountain regions in 2010, based on gridded population data (Jones and O'Neill, 2016; Gao, 2019) and a distance of less than 100 km from glaciers or permafrost located in mountains areas as defined in Figure 2.1. This population is expected to grow to 736–844 million across the shared socio-economic pathways by 2050. Many people living outside of mountain areas and not included in these numbers are also affected by changes in the mountain cryosphere. This chapter assesses recent and projected changes in glaciers, snow cover, permafrost and lake and river ice in high-mountain areas, their drivers, as well as their impact on the different services provided by the cryosphere and related adaptation, with a focus on literature published after the IPCC Fifth Assessment Report (AR5). The assessment of cryospheric change is focused on recent decades rather than a perspective over a longer period, and future changes spanning the 21st century. A paleo-perspective is covered in IPCC Sixth Assessment Report (AR6) Working Group I contribution on ‘The Physical Science Basis’. High mountain areas, as discussed here, include all mountain regions where glaciers, snow or permafrost are prominent features of the landscape, without a strict and quantitative demarcation, but with a focus on distinct regions (Figure 2.1). Mountain regions located in the polar regions are considered in Chapter 3 except those in Iceland, Scandinavia and Alaska and parts of adjacent Yukon Territory and British Columbia, which are included in this chapter. Many changes in the mountain environment are not solely or directly related to climate-change induced changes in the cryosphere, but to other direct or indirect effects of climate change, or to other consequences of socio-economic development. Consistent with the scope of this report with a focus on the ocean and the cryosphere, this section deals primarily with the impacts that can at least partially be attributed to cryosphere changes. Even though other drivers may be the dominant driver of change in many cases, they are not considered explicitly in this chapter, although unambiguous attribution to cryosphere changes is often difficult. Subject to Copyedit 2-7 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Figure 2.1: Distribution of mountain areas (orange shading) and glaciers (blue) as well as regional summary statistics for glaciers and permafrost in mountains. Mountains are distinguished based on a ruggedness index (>3.5), a logarithmically scaled measure of relative relief (Gruber, 2012). Eleven distinct regions with glaciers, generally corresponding to the primary regions in the Randolph Glacier Inventory, RGI v6.0 (RGI Consortium, 2017) are outlined, although some cryosphere related impacts presented in this chapter may go beyond these regions. Region names correspond to those in the RGI. Diamonds represent regional glacier area (RGI 6.0) and circles the permafrost area in all mountains within each region boundary (Obu et al., 2019). Histograms for each region show glacier and permafrost area in 200 m elevation bins as a percentage of total regional glacier/permafrost area, respectively. Also shown is the median elevation of the annual mean 0°C free-atmosphere isotherm calculated from the ERA-5 re-analysis of the European Centre for Medium Range Weather Forecasts over each region’s mountain area for the period 2006 to 2015, with 25–75% quantiles in grey. The annual 0°C isotherm elevation roughly separates the areas where precipitation predominantly falls as snow and rain. Areas above and below this elevation are loosely referred to as high and low elevations, respectively, in this chapter. 2.2 2.2.1 Changes in the Mountain Cryosphere Atmospheric Drivers of Changes in the Mountain Cryosphere Past changes of surface air temperature and precipitation in high-mountain areas have been documented by in-situ observations and regional reanalyses (Table SM2.2 and Table SM2.4). However, mountain observation networks do not always follow standard measurement procedures (Oyler et al., 2015; Nitu et al., 2018) and are often insufficiently dense to capture fine-scale changes (Lawrimore et al., 2011) and the underlying larger scale patterns. Future changes are projected using global (GCM) or regional (RCM) climate models or simplified versions thereof (e.g., Gutmann et al., 2016), used to represent processes at play in a dynamically consistent manner, and to relate mountain changes to larger-scale atmospheric forcing Subject to Copyedit 2-8 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere based on physical principles. Existing mountain-specific model studies typically cover individual mountain ranges, and there is currently no initiative found, such as model inter-comparisons or coordinated model experiments, which specifically and comprehensively addresses high mountain meteorology and climate globally. This makes it difficult to provide a globally uniform assessment. 2.2.1.1 Surface Air Temperature Mountain surface air temperature observations in Western North America, European Alps, High Mountain Asia show warming over recent decades at an average rate of 0.3°C per decade, with a likely range of ± 0.2°C, thereby outpacing the global warming rate 0.2 ± 0.1 °C per decade, (IPCC, 2018). Underlying data from global and regional studies are compiled in Table SM2.2, and Figure 2.2 provides a synthesis on mountain warming trends, mostly based on studies using in-situ observations. Local warming rates depend on the season (high confidence). For example, in the European Alps, warming has been found to be more pronounced in summer and spring (Auer et al., 2007; Ceppi et al., 2012), while on the Tibetan Plateau warming is stronger in winter (Liu et al., 2009; You et al., 2010). Studies comparing observations at lower and higher elevation at the global scale indicate that warming is generally enhanced above 500 m above sea level (a.s.l.) (e.g., Wang et al., 2016a; Qixiang et al., 2018, Table SM2.2). At the local and regional scale, evidence for elevation dependent warming, i.e. that the warming rate is different across elevation bands, is scattered and sometimes contradictory (Box 2.1). On the Tibetan Plateau, evidence based on combining insitu observations (often scarce at high elevation) with remote sensing and modelling approaches, indicates that warming is amplified around 4000 m a.s.l., but not above 5000 m a.s.l. (Qin et al., 2009; Gao et al., 2018). Studies in the Italian Alps (Tudoroiu et al., 2016) and Southern Himalaya (Nepal, 2016) have shown higher warming at lower elevation. Evidence from Western North and South America is conflicting (Table SM2.2). In other regions, evidence to assess whether warming varies with elevation is insufficient. In summary, there is medium evidence (medium agreement) that surface warming is different across elevation bands. Observed changes also depend on the type of temperature indicator: changes in daily mean, minimum and maximum temperature can display contrasting patterns depending on region, season and elevation (Table SM2.2). Attribution studies for changes in surface air temperature specifically in mountain regions are rare. Bonfils et al. (2008) and Dileepkumar et al. (2018) demonstrated that anthropogenic greenhouse gas emissions are the dominant factor in the recent temperature increases, partially compensated by other anthropogenic factors (land use change and aerosol emissions for Western USA and Western Himalaya, respectively). These findings are consistent with conclusions of AR5 regarding anthropogenic effects (Bindoff et al., 2013). It is thus likely that anthropogenic influence is the main contributor to surface temperature increases in highmountain regions since the mid-20th century, amplified by regional feedbacks. Until the mid-21st century, regardless of the climate scenario (Cross-Chapter Box 1 in Chapter 1), surface air temperature is projected to continue increasing (very high confidence) at an average rate of 0.3°C per decade, with a likely range of ± 0.2°C per decade, locally even more in some regions, generally outpacing global warming rates (0.2 ± 0.1 °C per decade; IPCC, 2018) (high confidence). Beyond mid-21st century, atmospheric warming in mountains will be stronger under a high greenhouse gas emission scenario (RCP8.5), and will stabilize at mid-21st levels under a low greenhouse gas emission scenario (RCP2.6), similar to global change patterns (very high confidence). The warming rate will result from the combination of regional (high confidence) and elevation-dependent (medium confidence) enhancement factors. Underlying evidence of future projections from global and regional studies is provided in Table SM2.3. Figure 2.3 provides examples of regional climate projections of surface air temperature, as a function of elevation and season (winter and summer) in North America (Rocky Mountains), South America (Subtropical Central Andes), Europe (European Alps) and High Mountain Asia (Hindu Kush and Karakoram, and Himalaya), based on global and regional climate projections. Subject to Copyedit 2-9 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Figure 2.2: Synthesis of trends in mean annual surface air temperature in mountain regions, reported in 40 studies based on 8703 observation stations in total (partly overlapping). Each line refers to a warming rate from one study, averaged over the time period indicated by the extent of the line. Colors indicate mountain region (Figure 2.1), and line thickness the number of observation stations used. Detailed references are found in Table SM2.2, which also provides additional information on trends for individual seasons and other temperature indicators (daily minimum or maximum temperature). [START BOX 2.1 HERE] Box 2.1: Does Atmospheric Warming in the Mountains Depend on Elevation ? In mountain regions, surface air temperature generally tends to decrease with increasing elevation thus directly impacting how much of the precipitation falls as snow as opposed to rain. Therefore, changes in air temperature have different consequences for snow cover, permafrost and glaciers at different elevations. A number of studies have reported that trends in air temperature vary with elevation, a phenomenon referred to Subject to Copyedit 2-10 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere as elevation dependent warming (EDW; Pepin et al., 2015, and references therein), with potential consequences beyond those of uniform warming. EDW does not imply that warming is larger at higher elevation, and smaller at lower elevation, but it means that the warming rate (e.g., in ºC per decade) is not the same across all elevation bands. Although this concept has received wide attention in recent years, the manifestation of EDW varies by region, season and temperature indicator (e.g. daily mean, minimum or maximum temperature), meaning that a uniform pattern does not exist. The identification of the underlying driving mechanisms for EDW and how they combine is complex. Several physical processes contribute to EDW, and quantifying their relative contributions has remained largely elusive (Minder et al., 2018; Palazzi et al., 2019). Some of the processes identified are similar to those explaining the amplified warming in the polar regions (Chapter 3). For example, the sensitivity of temperature to radiative forcing is increased at low temperatures common in both polar and mountain environments (Ohmura, 2012). Because the relationship between specific humidity and downwelling radiation is non-linear, in a dry and cold atmosphere found at high elevation, any increase in atmospheric humidity due to temperature increase drives disproportionately large warming (Rangwala et al., 2013; Chen et al., 2014). Snow-albedo feedback plays an important role where the snow cover is in decline (Pepin and Lundquist, 2008; Scherrer et al., 2012), increasing the absorption of solar radiation which in turn leads to increased surface air temperature and further snow melt. Other processes are specific to the mountain environment. Especially in the tropics, warming can be enhanced at higher elevation by a reduction of the vertical temperature gradient, due to increased latent heat release above the condensation level, favored in a warmer and moister atmosphere (Held and Soden, 2006). The cooling effect of aerosols, which also cause solar dimming, is more pronounced at low elevation and reduced at high elevation (Zeng et al., 2015). While many mechanisms suggest that warming should be enhanced at high elevation, observed and simulated EDW patterns are usually more complex (Pepin et al., 2015, and references therein). Numerical simulations by global and regional climate models, which show EDW, need to be considered carefully because of intrinsic limitations due to potentially incomplete understanding and implementation of relevant physical processes, in addition to coarse grid spacing with respect to mountainous topography (Ménégoz et al., 2014; Winter et al., 2017). [END BOX 2.1 HERE] 2.2.1.2 Rainfall and Snowfall Past precipitation changes are less well quantified than temperature changes and are often more heterogeneous, even within mountain regions (Hartmann and Andresky, 2013). Regional patterns are characterized by decadal variability (Mankin and Diffenbaugh, 2015) and influenced by shifts in large scale atmospheric circulation (e.g., in Alaska; Winski et al., 2017). While mountain regions do not exhibit clear direction of trends in annual precipitation over the past decades (medium confidence that there is no trend), snowfall has decreased, at least in part due to higher temperatures, especially at lower elevation (Table SM2.4, high confidence). Future projections of annual precipitation indicate increases of the order of 5 to 20% over the 21st century in many mountain regions, including the Hindu Kush and Himalaya, East Asia, East Africa, the European Alps and the Carpathian region, and decreases in the Mediterranean and the Southern Andes (medium confidence, Table SM2.5). Changes in the frequency and intensity of extreme precipitation events vary according to season and region. For example, across the Himalayan-Tibetan Plateau mountains, the frequency and intensity of extreme rainfall events are projected to increase throughout the 21st century, particularly during the summer monsoon (Panday et al., 2015; Sanjay et al., 2017). This suggests a transition toward more episodic and intense monsoonal precipitation, especially in the easternmost part of the Himalayan chain (Palazzi et al., 2013). Increases in winter precipitation extremes are projected in the European Alps (Rajczak and Schär, 2017). At lower elevation, near term (2031-2050) and end of century (2081-2100) projections of snowfall all indicate a decrease, for all greenhouse gas emission scenarios (very high confidence). At higher elevation, where temperature increase is insufficient to affect rain/snow partitioning, total winter precipitation increases can lead to increased snowfall (e.g., Kapnick and Delworth, 2013; O’Gorman, 2014) (medium confidence). Subject to Copyedit 2-11 Total pages: 94 FINAL DRAFT 2.2.1.3 Chapter 2 IPCC SR Ocean and Cryosphere Other Meteorological Variables Atmospheric humidity, incoming shortwave and longwave radiation, and near-surface wind speed and direction also influence the high-mountain cryosphere. Detecting their changes and associated effects on the cryosphere is even more challenging than for surface air temperature and precipitation, both from an observation and modelling standpoint. Therefore, most simulation studies of cryosphere changes are mainly driven by temperature and precipitation (see, e.g., Beniston et al., 2018, and references therein). Atmospheric moisture content, which is generally increasing in a warming atmosphere (Stocker et al., 2013), affects latent and longwave heat fluxes (Armstrong and Brun, 2008) with implications for the timing and rate of snow and ice ablation, and in some areas changes in atmospheric moisture content could be a significant driver of cryosphere change (Harpold and Brooks, 2018). Short-lived climate forcers, such as sulphur and black carbon aerosols (You et al., 2013), reduce the amount of solar radiation reaching the surface, with potential impacts on snow and ice ablation. Solar brightening caused by declining anthropogenic aerosols in Europe since the 1980s was shown to have only a minor effect on atmospheric warming at high elevation (Philipona, 2013), and effects on the cryosphere were not specifically discussed. Wind controls preferential deposition of precipitation, post-depositional snow drift and affects ablation of snow and glaciers through turbulent fluxes. Near-surface wind speed has decreased on the Tibetan Plateau between the 1970s and the early 2000s, and stabilized or increased slightly thereafter (Yang et al., 2014a; Kuang and Jiao, 2016). This is consistent with existing evidence for a decrease in near-surface wind speed on mid-latitude continental areas since the mid-20th century (Hartmann et al., 2013). In general, the literature on past and future changes of near-surface wind patterns in mountain areas is very limited. 2.2.2 Snow Cover Snow on the ground is an essential and widespread component of the mountain cryosphere. It affects mountain ecosystems and plays a major role for mass movement and floods in the mountains. It plays a key role in nourishing glaciers and provides an insulating and reflective cover at their surface. It influences the thermal regime of the underlying ground, including permafrost, with implications for ecosystems. Climate change modifies key variables driving the onset and development of the snow cover (e.g., solid precipitation), and those responsible for its ablation (e.g., air temperature, radiation). The snow cover, especially in low-lying and mid-elevation areas of mountain regions, has long been identified to be particularly sensitive to climate change. The mountain snow cover is characterized by a very strong interannual and decadal variability, similar to its main driving force solid precipitation (Lafaysse et al., 2014; Mankin and Diffenbaugh, 2015). Observations spanning several decades are required to quantify trends. Long-term in-situ records are scarce in some regions of the world, particularly in High Mountain Asia, Northern Asia and South America (Rohrer et al., 2013). Satellite remote sensing provides new capabilities for monitoring mountain snow cover on regional scales. The satellite record length is often insufficient to assess trends (Bormann et al., 2018). Evidence of past changes from regional studies is provided in Table SM2.6. At lower elevation, there is high confidence that the mountain snow cover has generally declined in duration (on average by 5 snow cover days per decade, with a likely range from 0 to 10 days per decade), mean snow depth and accumulated mass (snow water equivalent) since the middle of the 20th century, with regional variations. At higher elevation, snow cover trends are generally insignificant (medium confidence) or unknown. Most of the snow cover changes can be attributed, at lower elevation, to more precipitation falling as liquid precipitation (rain) and to increases in melt at all elevations, mostly due to changes in atmospheric forcings, especially increased air temperature (Kapnick and Hall, 2012; Marty et al., 2017) which in turn are attributed to anthropogenic forcings at a larger scale (Section 2.2.1). Formal anthropogenic attribution studies provide similar conclusions in Western North America (Pierce et al., 2008; Najafi et al., 2017). Assessing the impact of the deposition of short-lived climate forcers on snow cover changes is an emerging issue (Skiles et al., 2018 and references therein). This concerns light absorbing particles, in particular, which include deposited aerosols such as black carbon, organic carbon and mineral dust, or microbial growth (Qian et al., 2015), although the role of the latter has not been specifically quantified. Due to their seasonally Subject to Copyedit 2-12 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere variable deposition flux and impact, and mostly episodic nature in case of dust deposition (Kaspari et al., 2014; Di Mauro et al., 2015), light absorbing particles contribute to interannual fluctuations of seasonal snow melt rate (Painter et al., 2018) (medium evidence, high agreement). There is limited evidence (medium agreement) that increases in black carbon deposition from anthropogenic and biomass burning sources have contributed to snow cover decline in the High Mountain Asia (Li et al., 2016; Zhang et al., 2018) and South America (Molina et al., 2015). Projected changes of mountain snow cover are studied based on climate model experiments, either directly from GCM or RCM output, or following downscaling and the use of snowpack models. These projections generally do not specifically account for future changes in the deposition rate of light absorbing particles on snow (or, if so, simple approaches have been used hitherto; e.g., Deems et al., 2013), so that future changes in snow conditions are mostly driven by changes in meteorological drivers assessed in Section 2.2.1. Evidence from regional studies is provided in Table SM2.7. Although existing studies in mountain regions do not use homogenous reference periods and model configurations, common future trends can be summarized as follows. At lower elevation in many regions such as the European Alps, Western North America, Himalaya and subtropical Andes, the snow depth or mass is projected to decline by 25% (likely range between 10 and 40%), between the recent past period (1986-2005) and the near future (2031-2050), regardless of the greenhouse gas emission scenario (Cross-Chapter Box 1 in Chapter 1). This corresponds to a continuation of the ongoing decrease in annual snow cover duration (on average 5 days per decade, with a likely range from 0 to 10). By the end of the century (2081-2100), reductions of up to 80% (likely range from 50 to 90%) are expected under RCP8.5, 50% (likely range from 30 to 70 %) under RCP4.5 and 30% (likely range from 10 to 40 %) under RCP2.6. At higher elevations, projected reductions are smaller (high confidence), as temperature increases at higher elevations affect the ablation component of snow mass evolution, rather than both the onset and accumulation components. The projected increase in wintertime snow accumulation may result in a net increase in winter snow mass (medium confidence). All elevation levels and mountain regions are projected to exhibit sustained interannual variability of snow conditions throughout the 21st century (high confidence). Figure 2.3 provides projections of temperature and snow cover in mountain areas in Europe, High Mountain Asia (Himalaya and Hindu Kush Karakoram), North America (Rockies) and South America (sub-tropical Central Andes), illustrating how changes vary with elevation, season, region, future time period and climate scenario. Subject to Copyedit 2-13 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Figure 2.3: Projected change (1986-2005 to 2031-2050 and 2080-2099) of mean winter (December-May; June-August in Subtropical Central Andes) snow water equivalent, winter air temperature and summer air temperature (June-August; December-February in Subtropical Central Andes) in five high-mountain regions for RCP8.5 (all regions) and RCP2.6 (European Alps and Subtropical Central Andes). Changes are averaged over 500 m (a,b,c) and 1000 m (d,e) elevation bands. The numbers in the lower right of each panel reflect the number of simulations (note that not all models provide snow water equivalent). For the Rocky Mountains, data from NA-CORDEX RCMs (25 km grid spacing) driven by CMIP5 GCMs were used (Mearns et al., 2017). For the European Alps, data from EURO-CORDEX RCMs (12 km grid spacing) driven by CMIP5 GCMs were used (Jacob et al., 2014). For the other regions, CMIP5 GCMs were used: Zazulie (2016) and Zazulie et al. (2018) for the Subtropical Central Andes, and Terzago et al. (2014) and Palazzi et al. (2017) for the Hindu Kush and Karakoram and Himalaya. The list of models used is provided in Table SM2.8. 2.2.3 Glaciers The high mountain areas considered in this chapter (Figure 2.1), including all glacier regions in the world except those in Antarctica, Greenland, the Canadian and Russian Arctic, and Svalbard (which are covered in Chapter 3) include ~170,000 glaciers covering an area of ~250,000 km2 (RGI Consortium, 2017) with a total ice volume of 87±15 mm sea-level equivalent (Farinotti et al., 2019). These glaciers span an elevation range from sea-level, for example in south-east Alaska, to >8000 m a.s.l. in the Himalaya and Karakoram, and occupy diverse climatic regions. Their mass budget is determined largely by the balance between snow accumulation and melt at the glacier surface, driven primarily by atmospheric conditions. Rapid changes in mountain glaciers have multiple impacts for social-ecological systems, affecting not only bio-physical properties such as runoff volume and sediment fluxes in glacier-fed rivers, glacier-related hazards, and global sea-level (Chapter 4) but also ecosystems and human livelihoods, socio-economic activities and sectors such as agriculture and tourism as well as other intrinsic assets such as cultural values. While glaciers worldwide have experienced considerable fluctuations throughout the Holocene driven by multidecadal variations of solar and volcanic activity, and changes in atmospheric circulation (Solomina et al., 2016), this Subject to Copyedit 2-14 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere section focuses on observed glacier changes during recent decades and changes projected for the 21st century (Cross-Chapter Box 6 in Chapter 2). Satellite and in-situ observations of changes in glacier area, length and mass show a globally largely coherent picture of mountain glacier recession in the last decades (Zemp et al., 2015), although annual variability and regional differences are large (Figure 2.4; very high confidence). The global trend is statistically significant despite considerable interannual and regional variations (Medwedeff and Roe, 2017). Since AR5’s global 2003-2009 estimate based on Gardner et al. (2013), several new estimates of globalscale glacier mass budgets have emerged using largely improved data coverage and methods (Bamber et al., 2018; Wouters et al., 2019; Zemp et al., 2019). These estimates combined with available regional estimates (Table 2.A.1) that the glacier mass budget of all mountain regions (excluding Antarctica, Greenland, the Canadian and Russian Arctic, and Svalbard) was very likely -490±100 kg m-2 yr-1 (-123±24 Gt yr-1) during the period 2006-2015 with most negative averages (less than -850 kg m-2 yr-1) in the Southern Andes, Caucasus/Middle East and Central Europe. High Mountain Asia shows the least negative mass budget (-150±110 kg m-2 yr-1, Figure 2.4), but variations within the region are large with most negative regional balance estimates in Nyainqentanglha, Tibet (-620±230 kg m-2 yr-1) and slightly positive balances in the Kunlun Mountains for the period 2000-2016 (Brun et al., 2017). Due to large ice extent, the total mass loss and corresponding contribution to sea level 2006-2015 is largest in Alaska, followed by the Southern Andes and High Mountain Asia (Table 2.A.1). Zemp et al. (2019) estimated an increase in mean global-scale glacier mass loss by ~30% between 1986-2005 and 2006 and 2015. Subject to Copyedit 2-15 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Figure 2.4: Glacier mass budgets for the eleven mountain regions assessed in this Chapter (Figure 2.1) and these regions combined. Mass budgets for the remaining polar regions are shown in Chapter 3, Figure 3.8. Regional time series of annual mass change are based on glaciological and geodetic balances (Zemp et al., 2019). Superimposed are multi-year averages by Wouters et al. (2019) based on the Gravity Recovery and Climate Experiment (GRACE), only shown for the regions with glacier area >3,000 km2. Estimates by Gardner et al. (2013) were used in AR5. Additional regional estimates available in some regions and shown here are listed in Table 2.A.1. Annual and time-averaged massbudget estimates include the errors reported in each study. Glacier areas (A) and volumes (V) are based on RGI Consortium (2017) and Farinotti et al. (2019), respectively. Red and blue bars on map refer to regional budgets averaged over the period 2006-2015 in units of kg m-2 yr-1 and mm sea-level equivalent (SLE) per year, respectively, and are derived from each region’s available mass-balance estimates (Appendix 2.A, Table 1). It is very likely that atmospheric warming is the primary driver for the global glacier recession (Marzeion et al., 2014; Vuille et al., 2018). There is limited evidence (high agreement) that human-induced increases in greenhouse gases have contributed to the observed mass changes (Hirabayashi et al., 2016). It was estimated that the anthropogenic fraction of mass loss of all glaciers outside Greenland and Antarctica increased from 25 ± 35% during 1851–2010 to 69 ± 24% during 1991–2010 (Marzeion et al., 2014). Other factors, such as changes in meteorological variables other than air temperature or internal glacier dynamics, have modified the temperature-induced glacier response in some regions (high confidence). For example, glacier mass loss over the last seven decades on a glacier in the European Alps was intensified by higher air moisture leading to increased long-wave irradiance and reduced sublimation (Thibert et al., 2018). Changes in air moisture have also been found to play a significant role in past glacier mass changes in Eastern Africa (Prinz et al., 2016), while an increase in shortwave radiation due to reduced cloud cover Subject to Copyedit 2-16 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere contributed to an acceleration in glacier recession in the Caucasus (Toropov et al., 2019). In the Tien Shan mountains changes in atmospheric circulation in the North Atlantic and North Pacific in the 1970s resulted in an abrupt reduction in precipitation and thus snow accumulation, amplifying temperature-induced glacier mass loss (Duethmann et al., 2015). Deposition of light absorbing particles, growth of algae and bacteria and local amplification phenomena such as the enhancement of particles concentration due to surface snow and ice melt, and cryoconite holes, have been shown to enhance ice melt (e.g., Ginot et al., 2014; Zhang et al., 2017; Williamson et al., 2019) but there is limited evidence and low agreement that long-term changes in glacier mass are linked to light absorbing particles (Painter et al., 2013; Sigl et al., 2018). Debris cover can modulate glacier melt but there is limited evidence on its role in recent glacier changes (Gardelle et al., 2012; Pellicciotti et al., 2015). Rapid retreat of calving outlet glaciers in Patagonia was attributed to changes in glacier dynamics (Sakakibara and Sugiyama, 2014). Departing from this global trend of glacier recession, a small fraction of glaciers have gained mass or advanced in some regions mostly due to internal glacier dynamics or, in some cases, locally restricted climatic causes. For example, in Alaska 36 marine-terminating glaciers exhibited a complex pattern of periods of significant retreat and advance during 1948–2012, highly variable in time and lacking coherent regional behaviour (McNabb and Hock, 2014). These fluctuations can be explained by internal retreatadvance cycles typical of tidewater glaciers that are largely independent of climate (Brinkerhoff et al., 2017). Irregular and spatially inconsistent glacier advances, for example, in Alaska, Iceland and Karakoram, have been associated with surge-type flow instabilities largely independent of changes in climate (Sevestre and Benn, 2015; Bhambri et al., 2017; Section 2.3.2). Regional-scale glacier mass gain and advances in Norway in the 1990s and in New Zealand between 1983 and 2008 have been linked to local increases in snow precipitation (Andreassen et al., 2005) and lower air temperatures (Mackintosh et al., 2017), respectively, caused by changes in atmospheric circulation. Advances of some glaciers in Alaska, the Andes, Kamchatka and the Caucasus were attributed to volcanic activity causing flow acceleration through enhanced meltwater at the ice-bed interface (Barr et al., 2018). Region-averaged glacier mass budgets have been nearly balanced in the Karakoram since at least the 1970s (Bolch et al., 2017; Zhou et al., 2017; Azam et al., 2018), while slightly positive balances since 2000 have been reported in the western Kunlun Shan, eastern Pamir, and the central and northern Karakoram mountains (Gardelle et al., 2013; Brun et al., 2017; Lin et al., 2017; Berthier and Brun, 2019). This anomalous behavior has been related to specific mechanisms countering the effects of atmospheric warming, for example, an increase in cloudiness (Bashir et al., 2017) and snowfall (Kapnick et al., 2014) spatially heterogeneous glacier mass balance sensitivity (Sakai and Fujita, 2017), feedbacks due to intensified lowland irrigation (de Kok et al., 2018), and changes in summer atmospheric circulation (Forsythe et al., 2017). There is medium evidence (high agreement) that recent glacier mass changes have modified glacier flow. A study covering all glaciers in High Mountain Asia showed glacier slowdown for regions with negative mass budgets since the 1970s and slightly accelerated glacier flow for Karakoram and West Kunlun regions where balances were close to balance (Dehecq et al., 2019). Waechter et al. (2015) report reduced flow velocities in the St. Elias Mountains in North America, especially in areas of rapid ice thinning near glacier termini. In contrast Mouginot and Rignot (2015) found complex ice flow patterns with simultaneous acceleration and deceleration for glaciers of the Patagonian Icefield as well as large interannual variability during the last three decades concurrent with general thinning of the icefield. [START CROSS-CHAPTER BOX 6 HERE] Cross-Chapter Box 6: Glacier Projections in Polar and High-mountain Regions Century-scale projections for all glaciers on Earth including those around the periphery of Greenland and Antarctica are presented here. Projections of the Greenland and Antarctic ice sheets are presented in Chapter 4. Future changes in glacier mass have global implications through their contribution to sea-level change (Chapter 4) and local implication, for example, by affecting fresh water resources (Section 2.3.1). Glacier decline can also lead to loss of paleoclimate information contained in glacier ice (Thompson et al., 2017). Subject to Copyedit 2-17 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere AR5 included projections of 21st century glacier evolution from four process-based global-scale glacier models (Slangen and Van De Wal, 2011; Marzeion et al., 2012; Giesen and Oerlemans, 2013; Bliss et al., 2014). Results have since been updated (Bliss et al., 2014; Slangen et al., 2017; Hock et al., 2019) using new glacier inventory data and/or climate projections, and projections from two additional models have been presented (Hirabayashi et al., 2013; Huss and Hock, 2015). These six models were driven by climate projections from 8 to 21 General Circulation Models (GCMs) from the Fifth Coupled Model Intercomparison Project (CMIP5) (Taylor et al., 2012) forced by various Representative Concentration Pathways (RCPs), and results are systematically compared in Hock et al. (2019). Based on these studies there is high confidence that glaciers in polar and high-mountain regions will lose substantial mass by the end of the century. Results indicate global glacier mass losses by 2100 relative to 2015 of 18% [likely range 11 to 25%] (mean of all projections with range referring to ± one standard deviation) for scenario RCP2.6 and 36% [likely range 26 to 47%] for RCP8.5, but relative mass reductions vary greatly between regions (Figure CB6.1). Projected end-of-century mean mass losses relative to 2015 tend to be largest in mountain regions dominated by smaller glaciers and relatively little ice cover, exceeding on average 80%, for example, in Central Europe, Caucasus/Middle East, Low Latitudes, and North Asia for RCP8.5 (see Figure 2.1 for region definitions). While these glaciers’ contribution to sea level is negligible their large relative mass losses have implications for streamflow (Section 2.3.1, FAQ 2.1). The magnitude and timing of these projected mass losses is assigned medium confidence because the projections have been carried out using relatively simple models calibrated with limited observations in some regions and diverging initial glacier volumes. For example, mass loss by iceberg calving and subaqueous melt processes that can be particularly important components of glacier mass budgets in polar regions (McNabb et al., 2015) have only been included in one global-scale study (Huss and Hock, 2015). In addition instability mechanisms that can cause rapid glacier retreat and mass loss are not considered (Dunse et al., 2015; Sevestre et al., 2018; Willis et al., 2018). The projected global-scale relative mass losses 2015 - 2100 correspond to a sea-level contribution of 94 [likely range 69 to 119] mm sea-level equivalent (SLE) corresponding to an average rate of 1.1 [likely range 0.8 to 1.4] mm SLE yr-1 for RCP2.6, and 200 [likely range 156 to 240] mm SLE, a rate of 2.4 [likely range 1.8 to 2.8] mm SLE yr-1 for RCP8.5, in addition to the sea-level contribution from the Greenland and Antarctic ice sheets (Chapter 4). Averages refer to the mean and ranges to ± one standard deviation of all simulations. For RCP2.6, rates increase only slightly until approximately year 2040 with a steady decline thereafter, as glaciers retreat to higher elevations and reach new equilibrium. In contrast, for RCP8.5, the sea-level contribution from glaciers increases steadily for most of the century, reaching an average maximum rate exceeding 3 mm SLE yr-1 (Hock et al., 2019). For both RCPs the polar regions are the largest contributors with projected mass reductions by 2100 relative to 2015 combined for the Antarctic periphery, Arctic Canada, the Greenland periphery, Iceland, Russian Arctic, Scandinavia and Svalbard ranging from 16% [likely range 9 to 23%] for RCP2.6 to 33% [likely range 22 to 44%] for RCP8.5. Due to extensive ice cover, these regions make up roughly 80% of the global sea-level contribution from glaciers by 2100. The global projections are similar to those reported in AR5 for the period 2081-2100 relative to 1986-2005, if differences in period length and domain are accounted for (AR5’s glacier estimates excluded the Antarctic periphery). The eleven mountain regions covered in Chapter 2 are likely to lose 22 to 44% of their glacier mass by 2100 relative to 2015 for RCP2.6 and 37 to 57% for RCP8.5. Worldwide many glaciers are expected to disappear by 2100 regardless emission scenario, especially in regions with smaller glaciers (very high confidence) (Rabatel et al., 2013; Huss and Fischer, 2016; Rabatel et al., 2017). The global-scale projections (Figure CB6.1) are consistent with results from regional-scale studies using more sophisticated models. Kraaijenbrink et al. (2017) projected mass losses for all glaciers in High Mountain Asia of 64 ± 5% (RCP8.5) by the end of the century (2071-2100) compared to 1996-2015. A highresolution regional glaciation model including ice dynamics indicated that by 2100 glacier volume in western Canada will shrink by ~70% (RCP2.6) to ~90% (RCP8.5) relative to 2005 (Clarke et al., 2015). Zekollari et al. (2019) projected that the glaciers in the European Alps will largely disappear by 2100 (94±4% mass loss relative to 2017) for RCP 8.5, while projected mass losses are 63±11% for RCP2.6. Subject to Copyedit 2-18 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere AR5 concluded with high confidence that due to a pronounced imbalance between current glacier mass and climate, glaciers are expected to further recede even in the absence of further climate change. Studies since AR5 agree and provide further evidence (Mernild et al., 2013; Marzeion et al., 2018). Figure CB6.1: Projected glacier mass evolution between 2015 and 2100 relative to each region’s glacier mass in 2015 (100%) based on three RCP emission scenarios (Cross-Chapter Box 1 in Chapter 1). Thick lines show the averages of 46 to 88 model projections based on four to six glacier models for the same RCP, and the shading marks ± 1 standard deviation (not shown for RCP4.5 for better readability). Global projections are shown excluding and including the Antarctic (A) and Greenland (G) periphery. Regional sealevel contributions are given for three RCPs for all regions with >0.5 mm SLE between 2015 and 2100. The Low Latitudes region includes the glaciers in (sub)tropical south and central America, eastern Africa and Indonesia. Region Alaska includes adjacent glaciers in the Yukon and British Columbia. Regions are sorted by glacier volume according to Farinotti et al. (2019). Data based on Marzeion et al. (2012); Giesen and Oerlemans (2013); Hirabayashi et al. (2013); Bliss et al. (2014); Huss and Hock (2015); Slangen et al. (2017). Modified from Hock et al. (2019). [END CROSS-CHAPTER BOX 6 HERE] 2.2.4 Permafrost This section assesses permafrost, but not seasonally frozen ground, in high-mountain areas. As mountains also exist in polar areas, some overlap exists between this section and Chapter 3. Observations of permafrost are scarce (Tables 2.1 and 2.2, PERMOS, 2016; Bolch et al., 2018) and unevenly distributed among and within mountain regions. Unlike glaciers and snow, permafrost is a subsurface phenomenon that cannot easily be observed remotely. As a consequence, its distribution and change are less understood than for Subject to Copyedit 2-19 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere glaciers or snow, and in many mountain regions it can only be inferred (Gruber et al., 2017). Permafrost thaw and degradation impact people via runoff and water quality (Section 2.3.1), hazards and infrastructure (Section 2.3.2) and greenhouse gas emissions (Box 2.2). AR5 and IPCC’s Special Report on ‘Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation’ (SREX) assessed permafrost change globally, but not separately for mountains. AR5 concluded that permafrost temperatures had increased in most regions since the early 1980s (high confidence), although warming rates varied regionally, and attributed this warming to increased air temperature and changes in snow cover (high confidence). The temperature increase for colder permafrost was generally greater than for warmer permafrost (high confidence). SREX found a likely warming of permafrost in recent decades and expressed high confidence that its temperatures will continue to increase. AR5 found decreases of northern high-latitude near surface permafrost for 2016–2035 to be very likely and a general retreat of permafrost extent for the end of the 21st century and beyond to be virtually certain. While some permafrost phenomena, methods of observation and scale issues in scenario simulations are specific to mountainous terrain, the basic mechanisms connecting climate and permafrost are the same in mountains and polar regions. Between 3.6 and 5.2 million km2 are underlain by permafrost in the eleven high-mountain regions outlined in Figure 2.1 (medium confidence) based on data from two modelling studies (Gruber, 2012; Obu et al., 2019). For comparison, this is 14–21 times the area of glaciers (Section 2.2.3) in these regions (Figure 2.1) or 27– 29% of the global permafrost area. The distribution of permafrost in mountains is spatially highly heterogeneous, as shown in detailed regional modelling studies (Boeckli et al., 2012; Bonnaventure et al., 2012; Westermann et al., 2015; Azócar et al., 2017; Zou et al., 2017). Permafrost in the European Alps, Scandinavia, Canada, Mongolia, the Tien Shan and the Tibetan Plateau has warmed during recent decades and some observations reveal ground-ice loss and permafrost degradation (high confidence). The heterogeneity of mountain environments and scarcity of long-term observations challenge the quantification of representative regional or global warming rates. A recent analysis finds that permafrost at 28 mountain locations in the European Alps, Scandinavia, Canada as well as High Mountain Asia and North Asia warmed on average by 0.19 ± 0.05 °C per decade between 2007 and 2016 (Biskaborn et al., 2019). Over longer periods, observations in the European Alps, Scandinavia, Mongolia, the Tien Shan and the Tibetan Plateau (see also Cao et al., 2018) show general warming (Table 2.1, Figure 2.5) and degradation of permafrost at individual sites (e.g., Phillips et al., 2009). Permafrost close to 0ºC warms at a lower rate than colder permafrost because ground-ice melt slows warming. Similarly, bedrock warms faster than debris or soil because of low ice content. For example, several European bedrock sites (Table 2.1) have warmed rapidly, by up to 1ºC per decade, during the past two decades. By contrast, total warming of 0.5– 0.8ºC has been inferred for the second half of the 20th century based on thermal gradients at depth in an ensemble of European bedrock sites (Isaksen et al., 2001; Harris et al., 2003). Warming has been shown to accelerate at sites in Scandinavia (Isaksen et al., 2007) and in mountains globally within the past decade (Biskaborn et al., 2019). During recent decades, rates of permafrost warming in the European Alps and Scandinavia exceeded values of the late 20th century (limited evidence, high agreement). The observed thickness of the active layer, the layer of ground above permafrost subject to annual thawing (see Glossary) and freezing, increased in the European Alps, Scandinavia (Christiansen et al., 2010), and on the Tibetan Plateau during the past few decades (Table 2.2), indicating permafrost degradation. Geophysical monitoring in the European Alps during approximately the past 15 years revealed increasing subsurface liquid water content (Hilbich et al., 2008; Bodin et al., 2009; PERMOS, 2016), indicating gradual ground-ice loss. During recent decades, the velocity of rock-glaciers in the European Alps exceeded values of the late 20th century (limited evidence, high agreement). Some rock glaciers, i.e. masses of ice-rich debris that show evidence of past or present movement, show increasing velocity as a transient response to warming and water input, although continued permafrost degradation would eventually inactivate them (Ikeda and Matsuoka, 2002). Rock-glacier velocities observed in the European Alps in the 1990s were on the order of a few decimetres per year and during approximately the past 15 years they often were about 2–10 times higher (Bodin et al., 2009; Lugon and Stoffel, 2010; PERMOS, 2016). Destabilisation, including collapse and rapid acceleration, has been documented (Delaloye et al., 2010; Buchli et al., 2013; Bodin et al., 2016). One Subject to Copyedit 2-20 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere particularly long time series shows velocities around 1960 just slightly lower than during recent years (Hartl et al., 2016). In contrast to nearby glaciers, no clear change in rock-glacier velocity or elevation was detected at a site in the Andes between 1955 and 1996 (Bodin et al., 2010). The majority of similar landforms investigated in the Alaska Brooks Range increased their velocity since the 1950s, while few others slowed down (Darrow et al., 2016). Decadal-scale permafrost warming and degradation are driven by air temperature increase and additionally affected by changes in snow cover, vegetation and soil moisture. Bedrock locations, especially when steep and free of snow, produce the most direct signal of climate change on the ground thermal regime (Smith and Riseborough, 1996), increasing the confidence in attribution. Periods of cooling, one or few years long, have been observed and attributed to extraordinary low-snow conditions (PERMOS, 2016). Extreme increases of active-layer thickness often correspond with summer heat waves (PERMOS, 2016) and permafrost degradation can be accelerated by water percolation (Luethi et al., 2017). Similarity and synchronicity of interannual to decadal velocity changes of rock glaciers within the European Alps (Bodin et al., 2009; Delaloye et al., 2010) and the Tien Shan (Sorg et al., 2015), suggests common regional forcing such as summer air temperature or snow cover. Because air temperature is the major driver of permafrost change, permafrost in high-mountain regions is expected to undergo increasing thaw and degradation during the 21st century, with stronger consequences expected for higher greenhouse gas emission scenarios (very high confidence). Scenario simulations for the Tibet Plateau until 2100 estimate permafrost area to be strongly reduced, for example by 22–64% for RCP2.6 and RCP8.5 and a spatial resolution of 0.5º (Lu et al., 2017). Such coarse-scale studies (Guo et al., 2012; Slater and Lawrence, 2013; Guo and Wang, 2016), however, are of limited use in quantifying changes and informing impact studies in steep terrain due to inadequate representation of topography (Fiddes and Gruber, 2012). Fine-scale simulations, on the other hand, are local or regional, limited in areal extent and differ widely in their representation of climate change and permafrost. They reveal regional and elevational differences of warming and degradation (Bonnaventure and Lewkowicz, 2011; Hipp et al., 2012; Farbrot et al., 2013) as well as warming rates that differ between locations (Marmy et al., 2016) and seasons (Marmy et al., 2013). While structural differences in simulations preclude a quantitative summary, these studies agree on increasing warming and thaw of permafrost for the 21st century and reveal increased loss of permafrost under stronger atmospheric warming (Chadburn et al., 2017). Permafrost thaw at depth is slow but can be accelerated by mountain peaks warming from multiple sides (Noetzli and Gruber, 2009) and deep percolation of water (Hasler et al., 2011). Near Mont Blanc in the European Alps, narrow peaks below 3850 m a.s.l. may lose permafrost entirely under RCP 8.5 by the end of the 21st century (Magnin et al., 2017). As ground-ice from permafrost usually melts slower than glacier ice, some mountain regions will transition from having abundant glaciers to having few and small glaciers but large areas of permafrost that is thawing (Haeberli et al., 2017). Table 2.1: Observed changes in permafrost mean annual ground temperature (MAGT) in mountain regions. Values are based on individual boreholes or ensembles of several boreholes. The MAGT refers to the last year in a period and is taken from a depth of 10–20 m unless the borehole is shallower. Region names refer to Figure 2.1. Numbers in brackets indicate how many sites are summarised for a particular surface type and area, the underscored value is an average. Elevation [m a.s.l.] Surface Type Global >1000 various (28) Central Europe (Alps) 2500–3000 debris or coarse blocks (>10) 3500–4000 bedrock (4) Scandinavia 1402–1505 moraine (3) Subject to Copyedit Period MAGT [ºC] MAGT trend [ºC per decade] Reference 2006–2017 not specified 0.2 ± 0.05 Biskaborn et al. (2019) 1987–2005 2006–2017 > –3 > –3 0.0–0.2 0.0–0.6 PERMOS (2016) Noetzli et al. (2018) 2008–2017 >–5.5 0.0–1.0 Pogliotti et al. (2015) Magnin et al. (2015) Noetzli et al. (2018) 1999–2009 0 to –0.5 0.0–0.2 Isaksen et al. (2011) 2-21 Total pages: 94 FINAL DRAFT 1500–1894 Chapter 2 bedrock (2) 1999–2009 High-mountain Asia (Tien Shan) ~3330 bare soil (2) 1974–2009 3500 meadow (1) 1992–2011 High-mountain Asia (Tibetan Plateau) 4530–4960 unknown (6) 2005–2016 ~4650 meadow (6) 2002–2012 ~4650 steppe (3) 2002–2012 ~4650 bare soil (1) 2003–2012 4500–5000 unknown (6) 2002–2011 North Asia (Mongolia) 1350–2050 steppe (6) 2000–2009 IPCC SR Ocean and Cryosphere –2.7 0.5 Christiansen et al. (2010) –0.5 to –0.1 –1.1 0.3–0.6 0.4 Zhao et al. (2010) Liu et al. (2017) –1.5 to –0.3 –1.52 to –0.41 –0.79 to –0.17 –0.22 –1.5 to –0.16 0.1–0.5 0.08–0.24 0.09–0.18 0.15 0.08–0.24 Noetzli et al. (2018) Wu et al. (2015) Wu et al. (2015) Wu et al. (2015) Peng et al. (2015) –0.06 to –1.54 0.2–0.3 Zhao et al. (2010) Table 2.2: Observed changes of active-layer thickness (ALT) in mountain regions. Numbers in brackets indicate how many sites are summarised for a particular surface type and area. Region names refer to Figure 2.1. Elevation Surface Period [m a.s.l.] Type Scandinavia 353–507 peatland (9) 1978–2006 1997–2006 Central Europe (Alps) 2500–2910 bedrock (4) 2000–2014 High Mountain Asia (Tien Shan) 3500 meadow (1) 1992–2011 High Mountain Asia (Tibetan Plateau) 4629–4665 meadow (6) 2002–2012 2002–2012 4638–4645 steppe (3) 2002–2012 bare soil 4635 (1) 4848 meadow 2006–2014 Subject to Copyedit ALT in last year [m] ALT trend [cm per decade] Reference ~0.65–0.85 7–13 13–20 Åkerman and Johansson (2008) 4.2–5.2 10–100 PERMOS (2016) 1.70 19 Liu et al. (2017) 2.11–2.32 2.54–3.03 3.38 34.8–45.7 39.6–67.2 18.9 Wu et al. (2015) Wu et al. (2015) Wu et al. (2015) 1.92–2.72 15.2–54 Lin et al. (2016) 2-22 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Ground temperature (°C) 0 -1 -2 -3 -4 Region Ground material European Alps Scandinavia Debris High-Mountain Asia Bedrock -5 1990 1995 2000 2005 2010 2015 Figure 2.5: Mean annual ground temperature from boreholes in debris and bedrock in the European Alps, Scandinavia and High-Mountain Asia. Temperatures differ between locations and warming trends can be interspersed by short periods of cooling. One location shows degrading of permafrost. Overall, the number of observed boreholes is small and most records are short. The depth of measurements is approximately 10 m, and years without sufficient data are omitted (Noetzli et al., 2018). 2.2.5 Lake and River Ice Based on limited evidence, AR5 reported shorter seasonal ice cover duration during the past decades (low confidence), however, did not specifically address changes in mountain lakes and rivers. Observations of extent, timing, duration and thickness of lake and river ice rely mostly on in-situ measurements (e.g. Sharma et al., 2019) and, increasingly on remote sensing (Duguay et al., 2014). Lake and river ice studies focusing specifically on mountain regions are rare but observations from lakes in the European Alps, Scandinavia, and the Tibetan Plateau show highly variable trends in ice cover duration during the past decades. For example, Cai et al. (2019) reported shorter ice cover duration for 40 lakes and longer duration for 18 lakes on the Tibetan Plateau during the period 2000-2017. Similarly, using microwave remote sensing, Du et al. (2017) found shorter ice cover duration for 43 out of 71 lakes >50 km2 including lakes on the Tibetan Plateau during 2002-2015, but only five of these had statistically significant trends (p < 0.05), due to large interannual variability. The variable trends in the duration of lake ice cover on the Tibetan Plateau between 2002 and 2015 corresponded to variable trends in surface water temperatures. Of 52 study lakes in this region, 31 lakes showed a mean warming rate of 0.055 ± 0.033 °C per year, and 21 lakes showed a mean cooling rate of -0.053 ± 0.038 °C per year during 2001-2012 (Zhang et al., 2014). Kainz et al. (2017) reported a significant (p < 0.05) increase in the interannual variability in ice cover duration for a Subject to Copyedit 2-23 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere subalpine lake in Austria during 1921-2015 in addition to a significant trend in later freeze on, earlier icebreak up and shorter ice cover duration. A significant (p < 0.05) trend towards shorter ice cover duration was found for another Austrian alpine lake during 1972-2015 (Niedrist et al., 2018). Highly variable trends were also found in the timing and magnitude of river ice jams during 1903-2015, as reported by Rokaya et al. (2018) for Canadian rivers, including rivers in the mountains. Most of the variability in river ice trends could be explained by variable water flow, in particular due to flow regulation. There is high confidence that air temperature and solar radiation are the most important drivers to explain observed changes of lake ice dynamics (Sharma et al., 2019). In mountainous regions where the interannual variability in ice cover duration is high, additional drivers become important, for example, morphometry, wind exposure, salinity, and hydrology, in particular hydrological processes driven by glaciers (Kropácek et al., 2013; Song et al., 2014; Yao et al., 2016; Gou et al., 2017). Despite high spatial and temporal variability in lake and river ice cover dynamics in mountain regions there is limited evidence (high agreement) that further air temperature increases will result in a general trend towards later freezing, earlier break-up, and shorter ice cover duration in the future (Gebre et al., 2014; Du et al., 2017). Overall, there is only limited evidence on changes in lake and river ice specifically in the mountains, indicating a trend, but not universally, towards shorter lake ice cover duration consistent with increased water temperature. [START BOX 2.2 HERE] Box 2.2: Local, Regional and Global Climate Feedbacks Involving the Mountain Cryosphere The cryosphere interacts with the environment and contributes to several climate feedbacks, most notably ones involving the snow cover, referred to as the snow albedo feedback. The presence or absence of snow on the ground drives profound changes in the energy budget of land surfaces, hence influencing the physical state of the overlying atmosphere (Armstrong and Brun, 2008). The reduction of snow on the ground, potentially amplified by aerosol deposition and modulated by interactions with the vegetation, increases the absorption of incoming solar radiation and leads to atmospheric warming. In mountain regions, this positive feedback loop mostly operates at the local scale and is seasonally variable, with most visible effects at the beginning and end of the snow season (Scherrer et al., 2012). Examples of other mechanisms contributing to local feedbacks are introduced in Box 2.1. At the regional scale, feedbacks associated with light-absorbing particles deposition and enhanced snow albedo feedback were shown to induce surface air warming (locally up to 2°C) (Ménégoz et al., 2014) with accelerated snow cover reduction (Ji, 2016; Xu et al., 2016), and may also influence the Asian monsoon system (Yasunari et al., 2015). However, many of these studies have considered so-called rapid adjustments, without changes in large scale atmospheric circulation patterns, because they used regional or global models constrained by large scale synoptic fields. In summary, regional climate feedbacks involving the high mountain cryosphere, particularly the snow albedo feedback, have only been detected in large mountain regions such as the Himalaya, using global and regional climate models (medium confidence). Global-scale climate feedbacks from the cryosphere remain largely unexplored with respect to the proportion originating from high-mountains. Although mountain topography affects global climate (e.g., Naiman et al., 2017), there is little evidence for mountain-cryosphere specific feedbacks, largely because of the limited spatial extent of the mountain cryosphere. The most relevant feedback probably relates to permafrost in mountains, which contain about 28% of the global permafrost area (Section 2.2.4). Organic carbon stored in permafrost can be decayed following thaw and transferred to the atmosphere as carbon dioxide or methane (Schuur et al., 2015). This self-reinforcing effect accelerates the pace of climate change and operates in polar (Section 3.4.1.2.3) and mountain areas alike (Mu et al., 2017; Sun et al., 2018a). In contrast to polar areas, however, there is limited evidence and low agreement on the total amount of permafrost carbon in mountains because of differences in upscaling and difficulties to distinguish permafrost and seasonally-frozen soils due to the lack of data. For example, on the Tibet Plateau, the top 3 m of permafrost are estimated to contain about 15 petagrams (Ding et al., 2016) and mountain soils with permafrost globally are estimated to contain approximately 66 petagrams of organic carbon (Bockheim and Munroe, 2014). At the same time, there is Subject to Copyedit 2-24 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere limited evidence and high agreement that the average density (kg C m-2) of permafrost carbon in mountains is lower than in other areas. For example, densities of soil organic carbon are low in the sub-arctic Ural (Dymov et al., 2015) and 1–2 orders of magnitude lower in subarctic Sweden (Fuchs et al., 2015) in comparison to lowland permafrost, and 50% lower in mountains than in steppe-tundra in Siberia and Alaska (Zimov et al., 2006). Some mechanisms of soil carbon decay and transfer to the atmosphere in mountains are similar to those in lowland areas, for example collapse following thaw in peatlands (Mu et al., 2016; Mamet et al., 2017), and some are specific to areas with steep slopes, for example drainage of water from thawing permafrost leading to soil aeration (Dymov et al., 2015). There is no global-scale analysis of the climate feedback from permafrost in mountains. Given that projections indicate increasing thaw and degradation of permafrost in mountains during the 21st century (very high confidence) (Section 2.2.4), a corresponding increase in greenhouse gas emissions can be anticipated but is not quantified. [END BOX 2.2 HERE] 2.3 Mountain Social-Ecological Systems: Impacts, Risks and Human Responses 2.3.1 Water Resources The mountain cryosphere is an important source of freshwater in the mountains themselves and in downstream regions. The runoff per unit area generated in mountains is on average approximately twice as high as in lowlands (Viviroli et al., 2011) making mountains a significant source of fresh water in sustaining ecosystem and supporting livelihoods in and far beyond the mountain ranges themselves. The presence of snow, glaciers, and permafrost generally exert a strong control on the amount, timing and biogeochemical properties of runoff (FAQ 2.1). Changes to the cryosphere due to climate change can alter fresh water availability with direct consequences for human populations and ecosystems. 2.3.1.1 Changes in River Runoff AR5 reported increased winter flows and a shift in timing towards earlier spring snowmelt runoff peaks during previous decades (robust evidence, high agreement). In glacier-fed river basins, it was projected that meltwater yields from glaciers will increase for decades in many regions but then decline (very high confidence). These findings have been further supported and refined by a wealth of new studies since AR5. Recent studies indicate considerable changes in the seasonality of runoff in snow and glacier dominated river basins (very high confidence; Table SM2.9). Several studies have reported an increase in average winter runoff over the past decades, for example in western Canada (Moyer et al., 2016), the European Alps (Bocchiola, 2014; Bard et al., 2015) and Norway (Fleming and Dahlke, 2014), due to more precipitation falling as rain under warmer conditions. Summer runoff has been observed to decrease in basins, for example in western Canada (Brahney et al., 2017) and the European Alps (Bocchiola, 2014), but to increase in several basins in High Mountain Asia (Mukhopadhyay and Khan, 2014; Duethmann et al., 2015; Reggiani and Rientjes, 2015; Engelhardt et al., 2017). Both increases, for example, in Alaska (Beamer et al., 2016) and the Tien Shan (Wang et al., 2015; Chen et al., 2016), and decreases, for example, in western Canada (Brahney et al., 2017) have also been found for average annual runoff. In western Austria, Kormann et al. (2015) detected an increase in annual flow at high elevations and a decrease at low elevations between 1980-2010. These contrasting trends for summer and annual runoff often result from spatially variable changes in the contribution of glacier and snow melt. As glaciers shrink, annual glacier runoff typically first increases, until a turning point, often called “peak water” is reached, upon which runoff declines (FAQ 2.1). There is robust evidence and high agreement that peak water in glacier-fed rivers has already passed with annual runoff declining especially in mountain regions with predominantly smaller glaciers, for example, in the lowlatitude Andes (Frans et al., 2015; Polk et al., 2017), western Canada (Fleming and Dahlke, 2014; Brahney et al., 2017) and the Swiss Alps (Huss and Fischer, 2016). A global modelling study (Huss and Hock, 2018) suggests that peak water has been reached before 2019 for 82-95 % of the glacier area in the low latitude Andes, 40-49 % in Western Canada and USA, and 55-67 % in Central Europe and the Caucasus (Figure 2.6). Subject to Copyedit 2-25 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Projections indicate a continued increase in winter runoff in many snow and/or glacier-fed rivers over the 21st century (high confidence) regardless of the climate scenario, for example, in North America (Schnorbus et al., 2014; Sultana and Choi, 2018), central Europe (Addor et al., 2014; Bosshard et al., 2014), Scotland (Capell et al., 2014) and High Mountain Asia (Kriegel et al., 2013) due to increased winter snow melt and more precipitation falling as rain in addition to increases in precipitation in some basins (Table SM2.9). There is robust evidence (high agreement) that summer runoff will decline over the 21st century in many basins for all emission scenarios, for example, in western Canada and USA (Shrestha et al., 2017), the European Alps (Jenicek et al., 2018), High Mountain Asia (Prasch et al., 2013; Engelhardt et al., 2017) and the tropical Andes (Baraer et al., 2012), due to less snowfall and decreases in glacier melt after peak water. A global-scale projection suggests that decline in glacier runoff by 2100 (RCP8.5) may reduce basin runoff by 10 percent or more in at least one month of the melt season in several large river basins, especially in High Mountain Asia during dry seasons, despite glacier cover of less than a few percent (Huss and Hock, 2018). Projected changes in annual runoff in glacier dominated basins are complex including increases and decreases over the 21st century for all scenarios depending on the time period and the timing of peak water (high confidence) (Figure 2.6). Local and regional-scale projections in High Mountain Asia, Central Europe and Western Canada and USA suggest that peak water will generally be reached before or around the middle of the century. These finding are consistent with results from global-scale modelling of glacier runoff (Bliss et al., 2014; Huss and Hock, 2018) indicating generally earlier peak water in regions with little ice cover and smaller glaciers (e.g., Low Latitudes, central Europe and the Caucasus) and later peak water in regions with extensive ice cover and large glaciers (e.g., Alaska, Southern Andes). In some regions (e.g., Iceland) peak water from most glacier area is projected to occur earlier for RCP2.6 than RCP8.5, caused by decreasing glacier runoff as glaciers find a new equilibrium. In contrast melt-driven glacier runoff continues to rise for the higher emission scenario. There is very high confidence that spring peak runoff in many snow-dominated basins around the world will occur earlier in the year, up to several weeks, by the end of the century caused by earlier snow melt (e.g., Coppola et al., 2014; Bard et al., 2015; Yucel et al., 2015; Islam et al., 2017; Sultana and Choi, 2018). In addition to changes in ice and snow melt, changes in other variables such as precipitation and evapotranspiration due to atmospheric warming or vegetation change affect runoff amounts and timing (e.g., Bocchiola, 2014; Lutz et al., 2016). Changes in meltwater from ice and snow often dominates the runoff response to climate change at higher elevations, while changes in precipitation and evapotranspiration become increasingly important at lower elevations (Kormann et al., 2015). Permafrost thaw may affect runoff by releasing water from ground ice (Jones et al., 2018) and indirectly by changing hydrological pathways or ground water recharge as permafrost degrades (Lamontagne-Hallé et al., 2018). The relative importance of runoff from thawing permafrost compared to runoff from melting glaciers is expected to be greatest in arid areas where permafrost tends to be more abundant (Gruber et al., 2017). Because glaciers react more rapidly to climate change than permafrost, runoff in some mountain landscapes may become increasingly affected by permafrost thaw in the future (Jones et al., 2018). In summary, there is very high confidence that glacier and snow cover decline have affected and will continue to change the amounts and seasonality of river runoff in many snow-dominated and/or glacier-fed river basins. The average winter runoff is expected to increase (high confidence), and spring peak maxima will occur earlier (very high confidence). Although observed and projected trends in annual runoff vary substantially among regions and can even be opposite in sign, there is high confidence that average annual runoff from glaciers will have reached a peak, with declining runoff thereafter, at the latest by the end of the 21st century in most regions. The projected changes in runoff are expected to affect downstream water management, related hazards and ecosystems (Section 2.3.2, 2.3.4). Subject to Copyedit 2-26 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Figure 2.6: Timing of peak water from glaciers in different regions (Figure 2.1) under two emission scenarios (RCP2.6 and RCP8.5). Peak water refers to the year when annual runoff from the initially glacierized area will start to decrease due to glacier shrinkage after a period of melt-induced increase. The bars are based on Huss and Hock (2018) who used a global glacier model to compute the runoff of all individual glaciers in a region until year 2100 based on 14 GCMs. Depicted is the area of all glaciers that fall into the same 10-year peak water interval expressed as a percentage of each region's total glacier area, i.e., all bars for the same RCP sum up to 100% glacier area. Shadings of the bars distinguish different glacier sizes indicating a tendency for peak water to occur later for larger glaciers. Circles mark timing of peak Subject to Copyedit 2-27 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere water from individual case studies based on observations or modelling (Table SM2.10). Circles refer to results from individual glaciers regardless of size or a collection of glaciers covering <150 km2 in total, while triangles refer to regional-scale results from a collection of glaciers with >150 km2 glacier coverage. Case studies based on observations or scenarios other than RCP2.6 and RCP8.5 are shown in both the left and right set of panels. [START FAQ 2.1 HERE] FAQ 2.1: How does glacier shrinkage affect river runoff further downhill? Glaciers supply water that supports human communities both close to the glacier and far away from the glacier, for example for agriculture or drinking water. Rising temperatures cause mountain glaciers to melt and changes the water availability. At first, as the glacier melts, more water runs downhill away from the glacier. However, as the glacier shrinks, the water supply will diminish and farms, villages and cities might lose a valuable water source. Melting glaciers can affect river runoff, and thus freshwater resources available to human communities, not only close to the glacier but also far from mountain areas. As glaciers shrink in response to a warmer climate, water is released from long-term glacial storage. At first, glacier runoff increases because the glacier melts faster and more water flows downhill from the glacier. However, there will be a turning point after several years or decades, often called ‘peak water’, after which glacier runoff and hence its contribution to river flow downstream will decline (FAQ 2.1; Figure 1a). Peak water runoff from glaciers can exceed the amount of initial yearly runoff by 50 percent or more. This excess water can be used in different ways, such as for hydropower or irrigation. After the turning point, this additional water decreases steadily as the glacier continues to shrink, and eventually stops when the glacier has disappeared, or retreated to higher elevations where it is still cold enough for the glacier to survive. As a result, communities downstream lose this valuable additional source of water. Total amounts of river runoff will then depend mainly on rainfall, snow melt, ground water and evaporation. Furthermore, glacier decline can change the timing in the year and day when the most water is available in rivers that collect water from glaciers. In mid- or high latitudes, glacier runoff is greatest in the summer, when the glacier ice continues to melt after the winter snow has disappeared (FAQ 2.1, Figure 1b-d), and greatest during the day when air temperature and solar radiation are at their highest (FAQ 2.1, Figure 1e-g). As peak water occurs, more intense glacier melt rates also increase these daily runoff maxima significantly. In tropical areas, such as parts of the Andes, seasonal air temperature variations are small, and alternating wet and dry seasons are the main control on the amount and timing of glacier runoff throughout the year. The effects of glaciers on river runoff further downhill depend on the distance from the glacier. Close to the glaciers (e.g., within several kilometres), initial increases in yearly glacier runoff until peak water followed by decreases can affect water supply considerably, and larger peaks in daily runoff from the glaciers can cause floods. Further away from the glaciers the impact of glacier shrinkage on total river runoff tends to become small or negligible. However, the melt water from glaciers in the mountains can be an important source of water in hot and dry years or seasons when river runoff would otherwise be low, and thereby also reducing variability in total river runoff from year to year, even hundreds of kilometres away from the glaciers. Other components of the water cycle such as rainfall, evaporation, groundwater and snow melt can compensate or strengthen the effects of changes in glacier runoff as the climate changes. Subject to Copyedit 2-28 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere FAQ 2.1, Figure 1: A simplified overview of changes in runoff from a river basin with large (e.g., >50%) glacier cover as the glaciers shrink, showing the relative amounts of water from different sources - glaciers, snow (outside the glacier), rain and groundwater. Three different time scales are shown: annual runoff from the entire basin (upper panel); runoff variations over one year (middle panel) and variations during a sunny then a rainy summer day (lower panel). Note that seasonal and daily runoff variations are different before, during and after peak flow. The glacier’s initial negative annual mass budget becomes more negative over time until eventually the glacier has melted away. This is a simplified figure so permafrost is not addressed specifically and the exact partitioning between the different sources of water will vary between river basins. [END FAQ 2.1 HERE] 2.3.1.2 Water Quality Glacier decline can influence water quality by accelerating the release of stored anthropogenic legacy pollutants, with impacts to downstream ecosystem services. These legacy pollutants notably include persistent organic pollutants (POPs), particularly polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT), polycyclic aromatic hydrocarbons, and heavy metals (Hodson, 2014) and are associated with the deposition and release of black carbon. There is limited evidence that some of these pollutants found in surface waters in the Gangetic Plain during the dry season originate from Himalayan Subject to Copyedit 2-29 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere glaciers (Sharma et al., 2015), and glaciers in the European Alps store the largest known quantity of POPs in the Northern Hemisphere (Milner et al., 2017). Although their use has declined or ceased worldwide, polychlorinated biphenyls have been detected in runoff from glacier melt due to the lag time of release from glaciers (Li et al., 2017). Glaciers also represent the most unstable stores of DDT in European and other mountain areas flanking large urban centres and glacier-derived DDT is still accumulating in lake sediments downstream from glaciers (Bogdal et al., 2010). However, bioflocculation (the aggregation of dispersed organic particles by the action of organisms) can increase the residence time of these contaminants stored in glaciers thereby reducing their overall toxicity to freshwater ecosystems (Langford et al., 2010). Overall the effect on freshwater ecosystems of these contaminants is estimated to be low (medium confidence) (Milner et al., 2017). Of the heavy metals, mercury is of particular concern and an estimated 2.5 tonnes has been released by glaciers to downstream ecosystems across the Tibetan Plateau over the last 40 years (Zhang et al., 2012). Mercury in glacial silt, originating from grinding of rocks as the glacier flows over them, can be as large or larger than the mercury flux from melting ice due to anthropogenic sources deposited on the glacier (Zdanowicz et al., 2013). Both glacier erosion and atmospheric deposition contributed to the high rates of total mercury export found in a glacierized watershed in coastal Alaska (Vermilyea et al., 2017) and mercury output is predicted to increase in glacierized mountain catchments (Sun et al., 2017; Sun et al., 2018b) (medium confidence). However, a key issue is how much of this glacier-derived mercury, largely in the particulate form, is converted to toxic methyl mercury downstream. Methyl mercury can be incorporated into aquatic food webs in glacier streams (Nagorski et al., 2014) and bio-magnify up the food chain (Lavoie et al., 2013). Water originating from rock glaciers can also contribute other heavy metals that exceed guideline values for drinking water quality (Thies et al., 2013). In addition, permafrost degradation can enhance the release of other trace elements (e.g., aluminium, manganese and nickel) (Colombo et al., 2018). Indeed, projections indicate that all scenarios of future climate change will enhance the mobilisation of metals in metamorphic mountain catchments (Zaharescu et al., 2016). The release of toxic contaminants, particularly where glacial melt waters are used for irrigation and drinking water in the Himalayas and the Andes, is potentially harmful to human health both now and in the future (Hodson, 2014) (medium confidence). Soluble reactive phosphorus concentrations in rivers downstream of glaciers are predicted to decrease with declining glacier coverage (Hood et al., 2009) as a large percentage is associated with glacier-derived suspended sediment (Hawkings et al., 2016). In contrast, dissolved organic carbon (DOC), dissolved inorganic nitrogen and dissolved organic nitrogen concentrations in pro-glacial rivers is projected to increase this century due to glacier shrinkage (Hood et al., 2015; Milner et al., 2017) (robust evidence, medium agreement). Globally, mountain glaciers are estimated to release about 0.8 Tera g yr-1 (Li et al., 2018) of highly bioavailable DOC that may be incorporated into downstream food webs (Fellman et al., 2015; Hood et al., 2015). Loss rates of DOC from glaciers in the high mountains of the Tibetan Plateau were estimated to be ∼0.19 Tera g C yr-1, (Li et al., 2018) higher than other regions suggesting that DOC is released more efficiently from Asian mountain glaciers (Liu et al., 2016). Glacier DOC losses are expected to accelerate as they shrink, leading to a cumulative annual loss of roughly 15 Tera g C yr-1 of glacial dissolved organic carbon by 2050 from melting glaciers and ice-sheets (Hood et al., 2015). Permafrost degradation is also a major and increasing source of bioavailable DOC (Abbott et al., 2014; Aiken et al., 2014). Major ions calcium, magnesium, sulphate and nitrate (Colombo et al., 2018) are also released by permafrost degradation as well as acid drainage leaching into alpine lakes (Ilyashuk et al., 2018). Increasing water temperature has been reported in some high mountain streams (e.g., Groll et al., 2015; Isaak et al., 2016) due to decreases in glacial runoff, producing changes in water quality and species richness (Section 2.3.3). In contrast, water temperature in regions with extensive glacier cover are expected to show a transient decline, due to an enhanced cooling effect from increased glacial meltwater (Fellman et al., 2014). In summary, changes in the mountain cryosphere will cause significant shifts in downstream nutrients (DOC, nitrogen, phosphorus) and influence water quality through increases in heavy metals, particularly mercury, and other legacy contaminants (medium evidence, high agreement) posing a potential threat to human health. These threats are more focused where glaciers are subject to substantial pollutant loads such as High Mountain Asia and Europe, rather than areas like Alaska and Canada. Subject to Copyedit 2-30 Total pages: 94 FINAL DRAFT 2.3.1.3 Chapter 2 IPCC SR Ocean and Cryosphere Key Impacts and Vulnerability 2.3.1.3.1 Hydropower Hydropower comprises about 16% of electricity generation globally but close to 100%, in many mountainous countries (Hamududu and Killingtveit, 2012; IHA, 2018). It represents a significant source of revenue for mountainous regions (Gaudard et al., 2016). Due to the dependence on water resources as key input, hydropower operations are expected to be affected by changes in runoff from glaciers and snow cover (Section 2.3.1.1, FAQ 2.1). Both increases and decreases in annual and/or seasonal water input to hydropower facilities have been recorded in several high-mountain regions, for example, in Switzerland (Hänggi and Weingartner, 2012; Schaefli et al., 2019); Canada (Jost et al., 2012; Jost and Weber, 2013) Iceland (Einarsson and Jónsson, 2010) and High Mountain Asia (Ali et al., 2018). However, there is only limited evidence (medium agreement) that changes in runoff have led to changes in hydropower plant operation. For example, in Iceland, the National Power Company observed in 2005 that flows into their energy system were greater than historical flows. By incorporating the most recent runoff data into strategies for reservoir management it was possible to increase production capacity (Braun and Fournier, 2016). There is robust evidence (medium agreement) that water input to hydropower facilities will change in the future due to cryosphere-related impacts on runoff (Section 2.3.1.1). For example, in the Skagit river basin in British Columbia and northern Washington (Lee et al., 2016) and in California (Madani and Lund, 2010) projections (SRES A1B) show more runoff in winter and less in summer, and in India (Ali et al., 2018) snow and glacier runoff to hydropower plants is projected to decline in several basins. In some cases, catchments that are close together are projected to evolve in contrasting directions in terms of runoff, for example in the European Alps (Gaudard et al., 2013; Gaudard et al., 2014). Increased runoff due to changes in the cryosphere will increase the risk of overflows (non-productive discharge), particularly during winter and spring melt, with the greatest impacts on run-of-river power plants (e.g., in Canada; Minville et al., 2010; Warren and Lemmen, 2014) (medium confidence). There is medium evidence (high agreement) that changes in glacier- and moraine-dammed lakes, and changes in sediment supply will affect hydropower generation (Colonia et al., 2017; Hauer et al., 2018). Many glacier lakes have increased in volume, and can damage hydropower infrastructure when they empty suddenly (Engeset et al., 2005; Jackson and Ragulina, 2014; Carrivick and Tweed, 2016) (Section 2.3.2). If large enough, hydropower reservoirs can reduce the downstream negative impacts of changes in the cryosphere by storing and providing freshwater during hot, dry periods or by alleviating the effects of glacier floods (Jackson and Ragulina, 2014; Colonia et al., 2017). In mountain rivers, sediment volume and type depend on connectivity between hillslopes and the valley floor (Carrivick et al., 2013), glacier activity (Lane et al., 2017) and on water runoff regime feedbacks with river channel dynamics (Schmidt and Morche, 2006). An increase in suspended sediment loading under current reservoir operating policies is projected for some hydropower facilities, e.g., in British Columbia and northern Washington (Lee et al., 2016). Only a few studies have addressed the economic effects on hydropower due directly to changes in the cryosphere. For example in Peru, Vergara et al. (2007) studied the effect of both reduced glacier runoff and runoff with no glacier input once the glaciers have completely melted for the Carlton del Pato hydropower plant in Peru, and found an economic cost of between USD 5 and 20 million per year, with the lower figure for the cost of energy paid to the producer and the higher figure the society cost. Costs calculated for all of Peru, where ~80% of electricity comes from hydropower range from USD 60-212 million per year. If the cost of rationing energy is considered, the national cost is estimated as USD 1500 million per year. Other factors than changes in the cryosphere, such as market policies and regulation, may have greater significance for socio-economic development of hydropower in the future (Section 2.3.1.4, Gaudard et al., 2016). Hence, despite the efforts of hydropower agencies and regulatory bodies to quantify changes or to develop possible adaptation strategies (IHA, 2018), only a few organisations are incorporating current knowledge of climate change into their investment planning. The World Bank uses a decision tree approach to identify potential vulnerabilities in a hydropower project incurred from key uncertain factors and their combinations (Bonzanigo et al., 2015). Subject to Copyedit 2-31 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere 2.3.1.3.2 Agriculture High mountains have supported agricultural livelihoods for centuries. Rural communities are dependent on adequate levels of soil moisture at planting time, derived in part in many cases from irrigation water which includes glacier and snow meltwater; as a result, they are exposed to risk which stems from cryosphere changes (high confidence) (Figure 2.8). The relative poverty of many mountain communities contributes to their vulnerability to the impacts of these cryosphere changes (McDowell et al., 2014; Carey et al., 2017; Rasul and Molden, 2019) (medium evidence, high agreement). Glacier and snow melt water contribute irrigation water to adjacent lowlands as well. Pastoralism, an important livelihood strategy in mountain regions, is also impacted by cryosphere changes, but described in Section 2.3.6. There is medium evidence (medium agreement) that reduction in streamflow due to glacier retreat or reduced snow cover has led to reduced water availability for irrigation of crops and declining agricultural yields in several mountain areas, for example in the tropical Andes (Bury et al., 2011), High Mountain Asia (e.g., Nüsser and Schmidt, 2017), and the Rocky Mountains, USA (Frans et al., 2016; McNeeley, 2017; Table SM2.11). In addition to the effects on agriculture of changing availability of irrigation water, reductions in snow cover can also impact agriculture through its direct effects on soil moisture, as reported for Nepal, where lesser snow cover has led to the drying of soils and lower yields of potatoes and fodder (Smadja et al., 2015). Agriculture in high mountain areas is sensitive to other climatic driver as well. Rising air temperatures increase crop evapotranspiration, thus increasing water demand for crop production to maintain optimal yield (Beniston and Stoffel, 2014); they are also associated with upslope movement of cropping zones, which favours some farmers in high mountain areas, who are increasingly able to cultivate new crops, such as onions, garlic and apples in Nepal (Huntington et al., 2017; Hussain et al., 2018) and maize in Ecuador (Skarbø and VanderMolen, 2014). Dry spells and unseasonal frosts have also impacted agriculture in Peru (Bury et al., 2011). Adaptation activities in mountain agriculture related at least partially to cryospheric changes are detailed in Table SM2.12 and their geographic spread shown in Figure 2.9. Agriculture in these areas is sensitive to non-climate drivers as well, such as market forces and political pressures (Montana et al., 2016; Sietz and Feola, 2016; Figueroa-Armijos and Valdivia, 2017) and shifts in water governance (Rasmussen, 2016). The majority of the adaptation activities are autonomous, though some are planned or carried out with support from national governments, non-governmental organizations (NGOs), or international aid organizations. Though many studies report on benefits from these activities which accrue to community members as increased harvests and income, systematic evaluations of these adaptation strategies are generally lacking. A range of factors, discussed below, place barriers which limit the scale and scope of these activities in the mountain agricultural sector, including a lack of finance and technical knowledge, low adaptive capacity within communities, ill-equipped state organizations, ambiguous property rights and inadequate institutional and market support (medium evidence, high agreement). Section 2.3.6 examines two other responses to decreasing irrigation water: wage labour migration, which often serves as an adaptation strategy, and displacement of entire communities, an indication of the limits to adaptation; this displacement is also due in some cases to natural hazards. To cope with the reduced water supplies, planted areas have been reduced in a number of different places in Nepal (Gentle and Maraseni, 2012; Sujakhu et al., 2016). Adaptation responses within irrigation systems include the adoption of new irrigation technologies or upgrading existing technologies, adopting water conservation measures, water rationing, constructing water storage infrastructure, and change in cropping patterns (Rasul et al., 2019; Figure 2.9). Water-delivery technologies which reduce loss are adopted in Chile (Young et al., 2010) and Peru (Orlove et al., 2019). Similarly, greenhouses have been adopted in Nepal (Konchar et al., 2015) to reduce evapotranspiration, and reduce frost damage, though limited access to finance is a barrier to these activities. Box 2.3 describes innovative irrigation practices in India. Local pastoral communities have responded to these challenges with techniques broadly similar to those in agricultural settings by expanding irrigation facilities, e.g. in Switzerland (Fuhrer et al., 2014). In addition to adopting new technologies, some water-users make investments to tap more distant sources of irrigation water. Cross-Chapter Box 3 in Chapter 1 discusses such efforts in northern Pakistan, where landslides, associated with cryosphere change, have also damaged irrigation systems. Subject to Copyedit 2-32 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere The adoption of new crops and varieties is an adaptation response found in several regions. Farmers in northwest India have increased production of lentils and vegetables, which provide important nutrients to the local diet, with support from government watershed improvement programs which help address decreased availability of irrigation water, though stringent requirements for participation in the programs have limited access by poor households to this assistance (Dame and Nüsser, 2011). Farmers who rely on irrigation in the Naryn River basin in Kyrgyzstan have shifted from the water-intensive fruits and vegetables to fodder crops such as barley and alfalfa, which are more profitable. Upstream communities, with greater access to water and more active local institutions, are more willing to experiment with new crops than those further downstream (Hill et al., 2017). In other areas, crop choices also reflect responses to rising temperatures along with new market opportunities such as the demand for fresh vegetables by tourists in Nepal (Konchar et al., 2015; Dangi et al., 2018) and the demand for roses in urban areas in Peru (SENASA, 2017). Indigenous Knowledge and Local Knowledge, access to local and regional seed supply networks, proximity to agricultural extension and support services also facilitate the adoption of new crops (Skarbø and VanderMolen, 2014). Local institutions and embedded social relations play a vital role in enabling mountain communities to respond to the impacts of climate-driven cryosphere change. Indigenous pastoral communities who have tapped into new water sources to irrigate new areas in Peru have also strengthened the control of access to existing irrigated pastures (Postigo, 2014) and Bolivia (Yager, 2015). In an example of indigenous populations in the USA, two tribes who share a large reservation in the northern Rockies rely on rivers which receive glacier meltwater to irrigate pasture, and to maintain fisheries, domestic water supplies, and traditional ceremonial practices. Tribal water managers have sought to install infrastructure to promote more efficient water use and to protect fisheries, but these efforts have been impeded by land and water governance institutions in the region and by a history of social marginalization (McNeeley, 2017). High mountain communities have sought new financial resources from wage labour (Section 2.3.7), tourism (Mukherji et al., 2019) and government sources to support adaptation activities. Local water user associations in Kyrgyzstan and Tajikistan have adopted less water-intensive crops and reorganized the use and maintenance of irrigation systems, investing government relief payments after floods (Stucker et al., 2012). Similar measures are reported from India and Pakistan (Dame and Mankelow, 2010; Clouse, 2016; Nüsser and Schmidt, 2017), Nepal (McDowell et al., 2013) and Peru (Postigo, 2014). In contrast, fewer adaptation measures have been adopted in Uzbekistan, due to low levels of capital availability and to agricultural policies, including centralized water management, crop production quotas and weak agricultural extension, which limit the response capacity of farmers (Aleksandrova et al., 2014). Lowland agricultural areas which receive irrigation water from rivers fed by glacier melt and snowmelt are projected to face negative impacts in some regions (limited evidence, high agreement). In the Rhone basin in Switzerland, many irrigated pasture areas are projected to face water deficits by 2050, under the A1B scenario (Fuhrer et al., 2014; Cross Chapter Box 1 in Chapter 1). For California and the southwestern USA, a shift to peak snowmelt earlier in the year would create more frequent floods, and a reduced ability of existing reservoirs to store water by 2050 under RCP8.5 (Pagán et al., 2016) and by 2100 under RCP2.6, RCP4.5 and RCP8.5 (Pathak et al., 2018). The economic values of these losses have been estimated at USD 10.8 – 48.6 billion by around 2050 (Sturm et al., 2017). A similar transition to runoff peaks earlier in the year by 2010 under RCP2.6, RCP4.5 and RCP8.5, creating challenges for management of irrigation water, has been reported for the countries in central Asia which are dependent on snowcover and glaciers of the Tien Shan (Xenarios et al., 2018). In India and Pakistan, where over 100 million farmers receive irrigation from the Indus and Ganges Rivers, which also have significant inputs from glaciers and snowmelt, also face risks of decreasing water supplies from cryosphere change by 2100 (Biemans et al., 2019; Rasul and Molden, 2019). [START BOX 2.3 HERE] Box 2.3: Local Responses to Water Shortage in Northwest India Agriculture in Ladakh, a cold arid mountain region (~100,000 km2) in the western Himalaya of India with median elevation of 3350 m a.s.l. and mean annual precipitation of less than 100 mm, is highly dependent on streams for irrigation in the agricultural season in the spring and summer (Nüsser et al., 2012; Barrett and Subject to Copyedit 2-33 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Bosak, 2018). Glaciers in Ladakh, largely located at 5000-6000 m a.s.l. and small in size have retreated since at least since the late 1960s although less pronounced than in many other Himalayan regions (Chudley et al., 2017; Schmidt and Nüsser, 2017). However, the effect of glaciers on streamflow in Ladakh is poorly constrained, and measurements on changes in runoff and snow cover are lacking (Nüsser et al., 2018). To cope with seasonal water scarcity at critical times for irrigation, villagers in the region have developed four types of artificial ice reservoirs: basins, cascades, diversions and a form known locally as ice stupas. All these types of ice reservoirs capture water in the autumn and winter, allowing it to freeze, and hold it until spring, when it melts and flows down to fields (Clouse et al., 2017; Nüsser et al., 2018). In this way, they retain a previously unused portion of the annual flow and facilitate its use to supplement the decreased flow in the following spring (Vince, 2009; Shaheen, 2016). Frozen basins are formed from water which is conveyed across a slope through channels and check dams to shaded surface depressions near the villages. Cascades and diversions direct water to pass over stone walls, slowing its movement and allowing it to freeze. Ice stupas direct water through pipes into fountains, where it freezes into conical shapes (Box 2.3 Figure 1). These techniques use local materials and draw on Local Knowledge (Nüsser and Baghel, 2016). A study examined 14 ice reservoirs, including ice stupas, and concluded that they serve as “site-specific water conservation strategies” and that they can be regarded as appropriate local technologies to reduce seasonal water scarcity at critical times (Nüsser et al., 2018). It listed the benefits of ice reservoirs as improved water availability in spring, reduction of seasonal water scarcity and resulting crop failure risks, and the possibility of growing cash crops. However, the study questioned their usefulness as a long-term adaptation strategy, because their operation depends on winter runoff and freeze-thaw cycles, both of which are sensitive to interannual variability, and often deviate from the optimum range required for effective functioning of the reservoirs. It also raised questions about the financial costs and labour requirements, which vary across the four types of ice reservoirs. Box 2.3, Figure 1: Ice stupas in Ladakh, India (Photo: Padma Rigzi) [END BOX 2.3 HERE] 2.3.1.3.3 Drinking water supply Only a few studies provide detailed empirical assessments of the effects of cryosphere change on the amounts of drinking water supply. Decreases in drinking water supplies due to reduced glacier and snow Subject to Copyedit 2-34 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere meltwater have been reported for rural areas in the Nepal Himalaya (McDowell et al., 2013; Dangi et al., 2018), but the tropical Andes have received the most attention, including both urban conglomerates and some rural areas, where water resources are especially vulnerable to climate change due to water scarcity and increased demands (Chevallier et al., 2011; Somers et al., 2018), amidst rapidly retreating glaciers (Burns and Nolin, 2014). The contribution of glacier water to the water supply of La Paz, Bolivia, between 1963 and 2006 was assessed at 15% annually and 27% during the dry season (Soruco et al., 2015), though rising as high as 86% during extreme drought months (Buytaert and De Bièvre, 2012). Despite a 50% area loss, the glacier retreat has not contributed to reduced water supplies for the city, because increased melt rates have compensated for reductions in glacier volume. However, for a complete disappearance of the glaciers, assuming no change in precipitation, a reduction in annual runoff by 12% and 24% in the dry season was projected (Soruco et al., 2015) similar to reductions projected by 2050 under a RCP8.5 scenario for a basin in southern Peru (Drenkhan et al., 2019). Huaraz and Huancayo in Peru are other cities with high average contribution of melt water to surface water resources (up to ~20%; Buytaert et al., 2017) and rapid glacier retreat in their headwaters (Rabatel et al., 2013). Overall, risks to water security and related vulnerabilities are highly heterogeneous varying even at small spatial scales with populations closer to the glaciers being more vulnerable, especially during dry months and droughts (Buytaert et al., 2017; Mark et al., 2017). A regional-scale modelling study including all of Bolivia, Ecuador and Peru (Buytaert et al., 2017) estimated that roughly 390,000 domestic water users, mostly in Peru, rely on a high (>25%) long-term average contribution from glacier melt, with this number rising to almost 4 million in the driest month of a drought year. Despite high confidence in declining longer-term melt water contributions from glaciers in the tropical Andes (Figure CB6.1), major uncertainties remain how these will affect future human water use. Regional-scale water balance simulations forced by multi-model climate projections (Buytaert and De Bièvre, 2012), suggest a relatively limited effect of glacier retreat on water supply in four major cities (Bogota, La Paz, Lima, Quito) due to the dominance of human factors influencing water supply (Carey et al., 2014; Mark et al., 2017; Vuille et al., 2018), though uncertainties are large. Population growth and limited funding for infrastructure maintenance exacerbate water scarcity, though water managers have established programs in Quito and in Huancayo and the Santa and Vilcanota basins (Peru) to improve water management through innovations in grey infrastructure and ecosystem-based adaptations (Buytaert and De Bièvre, 2012; Buytaert et al., 2017; Somers et al., 2018). In summary, there is limited evidence (medium agreement) that glacier decline places increased risks to drinking water supply. In the Andes future increases in water demand due to population growth and other socio-economic stressors are expected to outpace the impact of climate change induced changes on water availability regardless the emission scenario. 2.3.1.4 Water Governance and Response Measures Cryospheric changes induced by climate change, and their effects on hydrological regime and water availability, bear relevance for the management and governance of water as a resource for communities and ecosystems (Hill, 2013; Beniston and Stoffel, 2014; Carey et al., 2017), particularly in areas where snow and ice contribute significantly to river runoff (medium confidence) (Section 2.3.1.1). In river basins influenced by glacier melt, changes in the cryosphere increase the variability of water availability (Figure 2.6). However, water availability is one aspect relevant for water management and governance, given that multiple and diverse decision-making contexts and governance approaches and strategies can influence how the water resource is accessed and distributed (medium confidence) (De Stefano et al., 2010; Beniston and Stoffel, 2014). A key risk factor that influences how water is managed and governed, rests on existing and unresolved conflicts that may or may not necessarily arise exclusively from demands over shared water resources, raising tensions within and across borders in river basins influenced by snow and glacier melt (ValdésPineda et al., 2014; Bocchiola et al., 2017). For example, in Central Asia, competing demand for water for hydropower and irrigation between upstream and downstream countries has raised tensions (Bernauer and Siegfried, 2012; Bocchiola et al., 2017). Similarly, competing demand for water is also reported in Chile (Valdés-Pineda et al., 2014) and in Peru (Vuille, 2013; Drenkhan et al., 2015). Since AR5, some studies have Subject to Copyedit 2-35 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere examined the impacts and risks related to projections of cryosphere-related changes in streamflow in transboundary basins in the 21st century, and suggest that these changes create barriers in effectively managing water in some settings (medium confidence). For instance, within the transnational Indus River basin, climate change impacts may reduce streamflow by the end of this century, thus putting pressure on established water sharing arrangements between nations (Jamir, 2016) and sub-national administrative units (Yang et al., 2014b). In this basin, management efforts may be hampered by current legal and regulatory frameworks for evaluating new dams, which do not take into account changes in streamflow that may result from climate change (Raman, 2018). Within the transnational Syr Darya and Amu Darya basins in Central Asia, competition for water between multiple uses, exacerbated by reductions in flow later in this century, may hamper future coordination (Reyer et al., 2017; Yu et al., 2019). However, other evidence from Central Asia suggests that relative water scarcity may not be the only factor to exacerbate conflict in this region (Hummel, 2017). Overall, there is medium confidence in the ability to meet future water demands in some mountain regions, given the combined uncertainties associated with accurate projections of water supply in terms of availability and the diverse socio-cultural and political contexts in which decisions on water access and distribution are taken. Since AR5, several studies highlight that integrated water management approaches, focused on the multipurpose use of water that includes water released from the cryosphere, which are important as adaptation measures, particularly for sectors reliant on this water source to sustain energy production, agriculture, ecosystems and drinking water supply (Figure 2.9). These measures, backed by effective governance arrangements to support them, demonstrate an ability to address increasing challenges to water availability arising from climate change in the mountain cryosphere, providing co-benefits through the optimization of storage and the release of water from high mountain reservoirs (medium confidence). Studies in Switzerland (e.g., Haeberli et al., 2016; Brunner et al., 2019), Peru (e.g., Barriga Delgado et al., 2018; Drenkhan et al., 2019), Central Asia (Jalilov et al., 2018) and Himalaya (Molden et al., 2014; Biemans et al., 2019) highlight the potential of water reservoirs in high mountains, including new reservoirs located in former glacier beds, alleviating seasonal water scarcity for multiple water usages. However, concerns are also raised in the environmental literature about their actual and potential negative impacts on local ecosystems and biodiversity hotspots, such as wetlands and peat bogs, which have been reported for small high mountain reservoirs e.g. in the European Alps (Evette et al., 2011) and for large dam construction projects in High Mountain Asia (e.g., Dharmadhikary, 2008). Transboundary cooperation at regional scales are reported to further support efforts that address the potential risks to water resources in terms of its availability and its access and distribution governance (Dinar et al., 2016). Furthermore, the UN 2030 Agenda and its Sustainable Development Goals (SDGs) (UN, 2015) may offer additional prospects to strengthen water governance under a changing cryosphere, given that monitoring and reporting on key water-related targets and indicators, and their interaction across other SDGs, direct attention to the provision of water as a key condition for development (Section 2.4). However, there is limited evidence to date to assess their effectiveness on an evidentiary basis. 2.3.2 Landslide, Avalanche and Flood Hazards High mountains are particularly prone to hazards related to snow, ice and permafrost as these elements exert key controls on mountain slope stability (Haeberli and Whiteman, 2015). This section assesses knowledge gained since previous IPCC reports, in particular SREX (e.g., Seneviratne et al., 2012), and AR5 Working Group II (Cramer et al., 2014). In this section, observed and projected changes in hazards are covered first, followed by exposure, vulnerability and resulting impacts and risks, and finally disaster risk reduction and adaptation. Cryospheric hazards that constitute tipping points are also listed in Table 6.1 in Chapter 6. Hazards assessed in this section range from localised effects on mountain slopes and adjacent valley floors (distance of reach of up to several kilometres) to events reaching far into major valleys and even surrounding lowlands (reach of tens to hundreds of kilometres), and include cascading events. Changes in the cryosphere due to climate change influence the frequency and magnitude of hazards, the processes involved, and the locations exposed to the hazards (Figure 2.7). Natural hazards and associated disasters are sporadic by nature, and vulnerability and exposure exhibit strong geographic variations. Assessments of change are based not only on direct evidence, but also on laboratory experiments, theoretical considerations and calculations, and numerical modelling. Subject to Copyedit 2-36 Total pages: 94 FINAL DRAFT 2.3.2.1 Chapter 2 IPCC SR Ocean and Cryosphere Observed and Projected Changes 2.3.2.1.1 Unstable slopes, landslides and glacier instabilities Permafrost degradation and thaw as well as increased water flow into frozen slopes can increase the rate of movement of frozen debris bodies, and lower their surface due to loss of ground ice (subsidence). Such processes affected engineered structures such as buildings, hazard protection structures, roads, or rail lines in all high mountains during recent decades (Section 2.3.4). Movement of frozen slopes and ground subsidence/heave are strongly related to ground temperature, ice content, and water input (Wirz et al., 2016; Kenner et al., 2017). Where massive ground ice gets exposed, retrogressive thaw erosion develops (Niu et al., 2012). The creep of rock glaciers (frozen debris tongues that slowly deform under gravity) is in principle expected to accelerate in response to rising ground temperatures, until substantial volumetric ice contents have melted out (Kääb et al., 2007; Arenson et al., 2015a). As documented for instance for sites in the European Alps and Scandinavia for recent years to decades, rock glaciers replenished debris-flow starting zones at their fronts, so that the intensified material supply associated with accelerated movement (Section 2.2.4) contributed to increased debris-flow activity (higher frequency, larger magnitudes) or slope destabilization, (Stoffel and Graf, 2015; Wirz et al., 2016; Kummert et al., 2017; Eriksen et al., 2018). There is high confidence that the frequency of rocks detaching and falling from steep slopes (rock fall) has increased within zones of degrading permafrost over the past half-century, for instance in high mountains in North America, New Zealand, and Europe (Allen et al., 2011; Ravanel and Deline, 2011; Fischer et al., 2012; Coe et al., 2017). Compared to the SREX and AR5 reports, the confidence in this finding increased. Available field evidence agrees with theoretical considerations and calculations that permafrost thaw increases the likelihood of rock fall (and also rock avalanches, which have larger volumes compared to rock falls) (Gruber and Haeberli, 2007; Krautblatter et al., 2013). These conclusions are also supported by observed ice in the detachment zone of previous events in North America, Iceland and Europe (Geertsema et al., 2006; Phillips et al., 2017; Sæmundsson et al., 2018). Summer heat waves have in recent years triggered rock instability with delays of only a few days or weeks in the European Alps (Allen and Huggel, 2013; Ravanel et al., 2017). This is in line with theoretical considerations about fast thaw of ice-filled frozen fractures in bedrock (Hasler et al., 2011) and other climate impacts on rock stability, such as from large temperature variations (Luethi et al., 2015). Similarly, permafrost thaw increased the frequency and volumes of landslides from frozen sediments in many mountain regions in recent decades (Wei et al., 2006; Ravanel et al., 2010; Lacelle et al., 2015). At lower elevations in the French Alps, though, climate-driven changes such as a reduction in number of freezing days is projected to lead to a reduction in debris flows (Jomelli et al., 2009). A range of slope instability types was found to be connected to glacier retreat (Allen et al., 2011; Evans and Delaney, 2015). Debris left behind by retreating glaciers (moraines) slid or collapsed, or formed fast flowing water-debris mixtures (debris flows) in recent decades, for instance in the European and New Zealand Alps (Zimmermann and Haeberli, 1992; Blair, 1994; Curry et al., 2006; Eichel et al., 2018). Over decades to millennia, or even longer, rock slopes adjacent to or formerly covered glaciers, became unstable, and, in some cases, eventually collapsed. Related, landslide activity increased in recently deglacierized zones in most high mountains (Korup et al., 2012; McColl, 2012; Deline et al., 2015; Kos et al., 2016; Serrano et al., 2018). For example, according to Cloutier et al. (2017) more than two-thirds of the large landslides that occurred in northern British Columbia between 1973 and 2003, occurred on cirque walls that have been exposed after glacier retreat from the mid-19th century on. Ice-rich permafrost environments following glacial retreat enhanced slope mass movements (Oliva and Ruiz-Fernández, 2015). At lower elevations, revegetation and rise of tree limit are able to stabilize shallow slope instabilities (Curry et al., 2006). Overall, there is high confidence that glacier retreat in general has in most high mountains destabilized adjacent debris and rock slopes over time scales from years to millennia, but robust statistics about current trends in this development are lacking. This finding reconfirms, and for some processes increases confidence in related findings from the SREX and AR5 reports. Ice break-off and subsequent ice avalanches are natural processes at steep glacier fronts. How climate-driven changes in geometry and thermal regime of such glaciers influenced ice avalanche hazards over years to decades depended strongly on local conditions, as shown for the European Alps (Fischer et al., 2013; Faillettaz et al., 2015). The few available observations are insufficient to detect trends. Where steep glaciers Subject to Copyedit 2-37 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere are frozen to bedrock, there is, however, medium evidence and high agreement from observations in the European Alps and from numerical simulations that failures of large parts of these glaciers were and will be facilitated in the future due to an increase in basal ice temperature (Fischer et al., 2013; Faillettaz et al., 2015; Gilbert et al., 2015) . In some regions, glacier surges constitute a recurring hazard, due to wide-spread, quasi-periodic and substantial increases in glacier speed over a period of a few months to years, often accompanied by glacier advance (Harrison et al., 2015; Sevestre and Benn, 2015). In a number of cases, mostly in North America and High Mountain Asia (Bevington and Copland, 2014; Round et al., 2017; Steiner et al., 2018), surgerelated glacier advances dammed rivers, causing major floods. In rare cases, glacier surges directly inundated agricultural land and damage infrastructure (Shangguan et al., 2016). Sevestre and Benn (2015) suggest that surging operates within a climatic envelope of temperature and precipitation conditions, and that shifts in these conditions can modify surge frequencies and magnitudes. Some glaciers have reduced or stopped surge activity, or are projected to do so within decades, as a consequence of negative glacier mass balances (Eisen et al., 2001; Kienholz et al., 2017). For such cases, also related hazards can be expected to decrease. In contrast, intensive or increased surge activity (Hewitt, 2007; Gardelle et al., 2012; Yasuda and Furuya, 2015) occurred in a region on and around the western Tibet plateau which exhibited no significant change or even positive glacier mass balances in recent decades (Brun et al., 2017). Enhanced melt-water production was suggested to be able to trigger or enhance surge-type instability, in particular for glaciers that contain ice both at the melting point and considerably below (Dunse et al., 2015; Yasuda and Furuya, 2015; Nuth et al., 2019). A rare type of glacier instability with large volumes (~ 107–108 m3) and high mobility (up to 200–300 km/h) results from the complete collapse of large sections of low-angle valley glaciers and subsequent combined ice/rock/debris avalanches. The largest of such glacier collapses have been reported in the Caucasus Mountains in 2002 (Kolka Glacier, ~130 fatalities) (Huggel et al., 2005; Evans et al., 2009), and in the Aru Range in Tibet in 2016 (twin glacier collapses with 9 fatalities) (Kääb et al., 2018). Whereas there is no evidence that climate change has played a direct role in the 2002 event, changes in glacier mass balance, water input into the glaciers, and the frozen regime of the glacier beds were involved in the 2016 collapses and at least partly linked with climate change (Gilbert et al., 2018). Besides the 2016 Tibet cases, it is unknown if such massive and rare collapse-like glacier instabilities can be attributed to climate change. 2.3.2.1.2 Snow avalanches Snow avalanches can occur either spontaneously due to meteorological factors such as loading by snowfall or liquid water infiltration following, e.g. surface melt or rain-on-snow, or can be triggered by the passage of people in avalanche terrain, the impact of falling ice or rocks, or by explosives used for avalanche control (Schweizer et al., 2003). There is no published evidence found, addressing the links between climate change and accidental avalanches triggered by recreationists or workers. Changes in snow-cover characteristics are expected to induce changes in spontaneous avalanche activity including changes in friction and flow regime (Naaim et al., 2013; Steinkogler et al., 2014). Ballesteros-Cánovas et al. (2018) reported increased avalanche activity in some slopes of the Western Indian Himalaya over the past decades related to increased frequency of wet-snow conditions. In the European Alps, avalanche numbers and runout distance have decreased with decreasing snow depth and increasing air temperature (Teich et al., 2012; Eckert et al., 2013). In the European Alps and Tatras mountains, over past decades, there has been a decrease in avalanche mass and run-out distance, a decrease of avalanches with a powder part since the 1980s, a decrease of avalanche numbers below 2000 m, and an increase above (Eckert et al., 2013; Lavigne et al., 2015; Gadek et al., 2017). A positive trend in the proportion of avalanches involving wet snow in December through February was shown for the last decades (Pielmeier et al., 2013; Naaim et al., 2016). Land use and land cover changes also contributed to changes in avalanches (GarcíaHernández et al., 2017; Giacona et al., 2018). Correlations between avalanche activity and the El NiñoSouthern Oscillation (ENSO) were identified from 1950 to 2011 in North and South America but there was no significant temporal trend reported for avalanche activity (McClung, 2013). Mostly inconclusive results were reported by Sinickas et al. (2015) and Bellaire et al. (2016) regarding the relationship between avalanche activity, climate change and disaster risk reduction activities in North America. In summary, in particular in Europe, there is medium confidence in an increase in avalanche activity involving wet snow, and a decrease in the size and run-out distance of snow avalanches over the past decades. Subject to Copyedit 2-38 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Future projections mostly indicate an overall decrease in snow depth and snow cover duration at lower elevation (Section 2.2.2), but the probability of occurrence of occasionally large snow precipitation events is projected to remain possible throughout most of the 21st century (Section 2.2.1). Castebrunet et al. (2014) estimated an overall 20 and 30% decrease of natural avalanche activity in the French Alps for the mid and end of the 21st century, respectively, under A1B scenario, compared to the reference period 1960–1990. Katsuyama et al. (2017) reached similar conclusions for Northern Japan, and Lazar and Williams (2008) for North America. Avalanches involving wet snow are projected to occur more frequently during the winter at all elevations due to surface melt or rain-on-snow (e.g., Castebrunet et al., 2014, for the French Alps), and the overall number and runout distance of snow avalanches is projected to decrease in regions and elevations experiencing significant reduction in snow cover (Mock et al., 2017). In summary, there is medium evidence and high agreement that observed changes in avalanches in mountain regions will be exacerbated in the future, with generally a decrease in hazard at lower elevation, and mixed changes at higher elevation (increase in avalanches involving wet snow, no clear direction of trend for overall avalanche activity). 2.3.2.1.3 Floods Glacier-related floods, including floods from lake outbursts (called glacier lake outburst floods or GLOFs), are documented for most glacierized mountain ranges and are among the most far-reaching glacier hazards. Past events affected areas tens to hundreds of kilometres downstream (Carrivick and Tweed, 2016). Retreating glaciers produced lakes at their fronts in many high-mountain regions margins in recent decades (Frey et al., 2010; Gardelle et al., 2011; Loriaux and Casassa, 2013). Lake systems in High Mountain Asia also often developed at the surface of downwasting, low-slope glaciers where they coalesced from temporally variable supraglacial lakes (Benn et al., 2012; Narama et al., 2017). Corroborating SREX and AR5 findings, there is high confidence that current global glacier shrinkage caused new lakes to form and existing lakes to grow in most regions, for instance in South America, High-Mountain Asia and Europe (Loriaux and Casassa, 2013; Paul and Mölg, 2014; Zhang et al., 2015; Buckel et al., 2018). Exceptions occurred and are expected to occur in the future for few lakes where evaporation, run-off and reduced meltwater influx in total led to a negative water balance (Sun et al., 2018a). Also, advancing glaciers temporarily dammed rivers, lake sections, or fjords (Stearns et al., 2015), for instance through surging (Round et al., 2017), causing particularly large floods once the ice dams breached. Outbursts from water bodies in and under glaciers are able to cause floods similar to those from surface lakes but little is known about the processes involved and any trends under climate change. In some cases, the glacier thermal regime played a role so that climate-driven changes in thermal regime are expected to alter the hazard potential, depending on local conditions (Gilbert et al., 2012). Another source of large water bodies under glaciers and subsequent floods has been subglacial volcanic activity (Section 2.3.2.1.4). There is also high confidence that the number and area of glacier lakes will continue to increase in most regions in the coming decades, and new lakes will develop closer to steep and potentially unstable mountain walls where lake outbursts can be more easily triggered by the impact of landslides (Frey et al., 2010; ICIMOD, 2011; Allen et al., 2016a; Linsbauer et al., 2016; Colonia et al., 2017; Haeberli et al., 2017). In contrast to the number and size of glacier lakes, trends in the number of glacier-related floods are not well known for the recent decades (Carrivick and Tweed, 2016; Harrison et al., 2018), although a number of phases of increased and decreased flood activity have been documented for individual glaciers in North America and Greenland, spanning decades (Geertsema and Clague, 2005; Russell et al., 2011). A decrease in moraine-dammed glacier lake outburst floods in recent decades suggests a response of lake outburst activity being delayed by some decades with respect to glacier retreat (Harrison et al., 2018) but inventories might significantly underestimate the number of events (Veh et al., 2018). For the Himalaya, Veh et al. (2019) found no increase in the number of glacier lake outburst floods since the late 1980s. The degradation of permafrost and the melting of ice buried in lake dams have been shown to lower dam stability and contribute to outburst floods in many high-mountain regions (Fujita et al., 2013; Erokhin et al., 2017; Narama et al., 2017). Floods originating from the combination of rapidly melting snow and intense rainfall, referred to as rain-onsnow events, are some of the most damaging floods in mountain areas (Pomeroy et al., 2016; Il Jeong and Sushama, 2018). The hydrological response of a catchment to a rain-on-snow event depends on the characteristics of the precipitation event, but also on turbulent fluxes driven by wind and humidity, which typically provide most of the melting energy during such events (Pomeroy et al., 2016), and the state of the Subject to Copyedit 2-39 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere snowpack, in particular the liquid water content (Würzer et al., 2016). An increase in the occurrence of rainon-snow events in high-elevation zones, and a decrease at the lowest elevations were reported (western USA, 1949–2003, McCabe et al. (2007); Oregon, 1986–2010, Surfleet and Tullos (2013); Switzerland, 1972–2016, Moran-Tejéda et al. (2016), central Europe, 1950–2010, Freudiger et al. (2014). These trends are consistent with studies carried out at the scale of the Northern Hemisphere (Putkonen and Roe, 2003; Ye et al., 2008; Cohen et al., 2015). There are no studies found on this topic in Africa and South America. In summary, evidence since AR5 suggests that rain-on-snow events have increased over the last decades at high elevations, particularly during transition periods from autumn to winter and winter to spring (medium confidence). The occurrence of rain-on-snow events has decreased over the last decade in low-elevation or low-latitude areas due to a decreasing duration of the snowpack, except for the coldest months of the year (medium confidence). Il Jeong and Sushama (2018) projected an increase in rain-on-snow events in winter and a decrease in spring, for the period 2041–2070 (RCP4.5 and RCP8.5) in North America, corroborated by Musselman et al. (2018). Their frequency in the Swiss Alps is projected to increase at elevations higher than 2000 m a.s.l. (SRES A1B, 2025, 2055, and 2085) (Beniston and Stoffel, 2016). This study showed that the number of rain-onsnow events may increase by 50%, with a regional temperature increase of 2°C to 4°C, and decrease with a temperature rise exceeding 4°C. In Alaska, an overall increase of rain-on-snow events is projected, however with a projected decline in the southwestern/southern region (Bieniek et al., 2018). In summary, evidence since AR5 suggests that the frequency of rain-on-snow events is projected to increase and occur earlier in spring and later in autumn at higher elevation and to decrease at lower elevation (high confidence). 2.3.2.1.4 Combined hazards and cascading events The largest mountain disasters in terms of reach, damage and lives lost that involve ice, snow and permafrost occurred through a combination or chain of processes. New evidence since SREX and AR5 have these findings (Anacona et al., 2015; Evans and Delaney, 2015). Some process chains occur frequently, while others are rare, specific to local circumstances and difficult to anticipate. Glacier lake outbursts were in many mountain regions and over recent decades documented to have been triggered by impact waves from snow-, ice- or rock-avalanches, landslides, iceberg calving events, or by temporary blockage of surface or subsurface drainage channels (Benn et al., 2012; Narama et al., 2017). Rock-slope instability and catastrophic failure along fjords caused tsunamis (Hermanns et al., 2014; Roberts et al., 2014). For instance, a landslide-generated wave in 2015 at Taan Fjord, Alaska, ran up 193 m on the opposite slope and then travelled more than 20 km down the fjord (Higman et al., 2018). Earthquakes have been a starting point for different types of cascading events, for instance by causing snow-, ice- or rock-avalanches, and landslides (van der Woerd et al., 2004; Podolskiy et al., 2010; Cook and Butz, 2013; Sæmundsson et al., 2018). Glaciers and their moraines, including morainic lake dams seem, however, not particularly prone to earthquake-triggered failure (Kargel et al., 2016). Landslides and rock avalanches in glacier environments were often documented to entrain snow and ice that fluidize, and incorporate additional loose glacial sediments or water bodies, thereby multiplying their mobility, volume and reach (Schneider et al., 2011; Evans and Delaney, 2015). Rock avalanches onto glaciers triggered glacier advances in recent decades, for instance in North America, New Zealand and Europe, mainly through reducing surface melt (Deline, 2009; Reznichenko et al., 2011; Menounos et al., 2013). In glacier-covered frozen rock walls, particularly complex thermal, mechanical, hydraulic and hydrologic interactions between steep glaciers, frozen rock and its ice content, and unfrozen rock sections lead to combined rock/ice instabilities that are difficult to observe and anticipate (Harris et al., 2009; Fischer et al., 2013; Ravanel et al., 2017). There is limited evidence of observed direct event chains to project future trends. However, from the observed and projected degradation of permafrost, shrinkage of glaciers and increase in glacier lakes it is reasonable to assume that event chains involving these could increase in frequency or magnitude, and that according hazard zones could expand. Volcanoes covered by snow and ice often produce substantial meltwater during eruptions. This typically results in floods and/or lahars (mixtures of meltwater and volcanic debris) which can be exceptionally violent and cause large-scale loss of life and destruction to infrastructure (Barr et al., 2018). The most devastating example from recent history occurred in 1985, when the medium-sized eruption of Nevado del Ruiz volcano, Colombia, produced lahars that killed more than 23,000 people some 70 km downstream (Pierson et al., 1990). Hazards associated with ice and snow-clad volcanoes have been reported mostly from Subject to Copyedit 2-40 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere the Cordilleras of the Americas, but also from the Aleutian arc (USA), Mexico, Kamchatka (Russia), Japan, New Zealand and Iceland (Seynova et al., 2017). In particular under Icelandic glaciers, volcanic activity and eruptions melted large amounts of ice and caused especially large floods if water accumulated underneath the glacier (Björnsson, 2003; Seneviratne et al., 2012). There is medium confidence that the overall hazard related to floods and lahars from ice- and snow-clad volcanoes will gradually diminish over years-to-decades as glaciers and seasonal snow-cover continue to decrease under climate change (Aguilera et al., 2004; Barr et al., 2018). On the other hand, shrinkage of glaciers may uncover steep slopes of unconsolidated volcanic sediments, thus decreasing in the future the resistance of these volcano flanks to heavy rain fall and increasing the hazard from related debris flows (Vallance, 2005). In summary, future changes in snow and ice are expected to modify the impacts of volcanic activity of snow and ice-clad volcanoes (high confidence) although in complex and locally variable ways and at a variety of time-scales (Barr et al., 2018; Swindles et al., 2018). Figure 2.7: Anticipated changes in high mountain hazards under climate change, driven by changes in snow cover, glaciers and permafrost, overlay changes in the exposure and vulnerability of individuals, communities, and mountain infrastructure. Subject to Copyedit 2-41 Total pages: 94 FINAL DRAFT 2.3.2.2 Chapter 2 IPCC SR Ocean and Cryosphere Exposure, Vulnerability and Impacts 2.3.2.2.1 Changes in exposure Confirming findings from SREX, there is high confidence that the exposure of people and infrastructure to cryosphere hazards in high-mountain regions has increased over recent decades, and this trend is expected to continue in the future (Figure 2.7). In some regions, tourism development has increased exposure, where often weakly regulated expansion of infrastructure such as roads, trails, and overnight lodging brought more visitors into remote valleys and exposed sites (Gardner et al., 2002; Uniyal, 2013). As an example for the consequences of increased exposure, many of the more than 350 fatalities resulting from the 2015 earthquake-triggered snow-ice avalanche in Langtang, Nepal, were foreign trekkers and their local guides (Kargel et al., 2016). Further, several thousand religious pilgrims were killed during the 2013 Kedarnath glacier flood disaster (State of Uttarakhand, Northern India) (Kala, 2014). The expansion of hydropower (Section 2.3.1) is another key factor, and in the Himalaya alone, up to two-thirds of the current and planned hydropower projects are located in the path of potential glacier floods (Schwanghart et al., 2016). Changes in exposure of local communities, for instance through emigration driven by climate-change related threats (Grau and Aide, 2007; Gosai and Sulewski, 2014), or increased connectivity and quality of life in urban centres (Tiwari and Joshi, 2015), are complex and vary regionally. The effects of changes in exposure on labour migration and relocation of entire communities are discussed in Section 2.3.6. 2.3.2.2.2 Changes in vulnerability Considering the wide-ranging social, economic, and institutional factors that enable communities to adequately prepare for, respond to, and recover from climate change impacts (Cutter and Morath, 2013), there is limited evidence and high agreement that mountain communities, particularly within developing countries, are highly vulnerable to the adverse effects of enhanced cryosphere hazards. There are few studies that have systematically investigated the vulnerability of mountain communities to natural hazards (Carey et al., 2017). Coping capacities to withstand impacts from natural hazards in mountain communities are constrained due to a number of reasons. Fundamental weather and climate information is lacking to support both short-term early warning for imminent disasters, and long-term adaptation planning (Rohrer et al., 2013; Xenarios et al., 2018). Communities may be politically and socially marginalised (Marston, 2008). Incomes are typically lower and opportunities for livelihood diversification restricted (McDowell et al., 2013). Emergency responders can have difficulties accessing remote mountain valleys after disasters strike (Sati and Gahalaut, 2013). Cultural or social ties to the land can limit freedom of movement (Oliver-Smith, 1996). Conversely, there is evidence that some mountain communities exhibit enhanced levels of resilience, drawing on long-standing experience, and Indigenous Knowledge and Local Knowledge gained over many centuries of living with extremes of climate and related disasters (Gardner and Dekens, 2006). In the absence of sufficient data, few studies have considered temporal trends in vulnerability (Huggel et al., 2015a). 2.3.2.2.3 Impacts on livelihoods Empirical evidence from past events shows that cryosphere-related landslides and floods can have severe impacts on lives and livelihoods, often extending far beyond the directly affected region, and persisting for several years. Glacier lake outburst floods alone have over the past two centuries directly caused at least 400 deaths in Europe, 5745 deaths in South America, and 6300 deaths in Asia (Carrivick and Tweed, 2016), although these numbers are heavily skewed by individual large events occurring in Huaraz and Yungay, Peru (Carey, 2005) and Kedarnath, India (Allen et al., 2016b). Economic losses associated with these events are incurred through two pathways. The first consists of direct losses due to the disasters, and the second includes indirect costs from the additional risk and loss of potential opportunities, or from additional investment that would be necessary to manage or adapt to the challenges brought about by the cryosphere changes. Nationwide economic impacts from glacier floods have been greatest in Nepal and Bhutan (Carrivick and Tweed, 2016). The disruption of vital transportation corridors that can impact trading of goods and services (Gupta and Sah, 2008; Khanal et al., 2015), and the loss of earnings from tourism can represent significant far-reaching and long-lasting impacts (Nothiger and Elsasser, 2004; IHCAP, 2017). The Dig Tsho flood in the Khumbu Himal of Nepal in 1985 damaged a hydropower plant and other properties, with estimated economic losses of USD 500 million (Shrestha et al., 2010). Less tangible, but equally important impacts concern the cultural and social disruption resulting from Subject to Copyedit 2-42 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere temporary or permanent evacuation (Oliver-Smith, 1979). According to the International Disaster Emergency Events Database (EM-DAT), over the period 1985–2014, absolute economic losses in mountain regions from all flood and mass movements (including non-cryosphere origins) were highest in the HinduKush Himalaya region (USD 45 billion), followed by the European Alps (USD 7 billion), and the Andes (USD 3 billion) (Stäubli et al., 2018). For example, a project to dig a channel in Tsho Rolpa glacier in Nepal that lowered a glacial lake cost USD 3 million in 2000 (Bajracharya, 2010), and similar measures have been taken at Imja Tsho Lake in Nepal in 2016 (Cuellar and McKinney, 2017). Other impacts are related to drinking and irrigation water and livelihoods (Section 2.3.1). In summary, there is high confidence that in the context of mountain flood and landslide hazards, exposure, and vulnerability growing in the coming century, significant risk reduction and adaptation strategies will be required to avoid increased impacts. 2.3.2.3 Disaster Risk Reduction and Adaptation There is medium confidence that applying an integrative socio-ecological risk perspective to flood, avalanche and landslide hazards in high-mountain regions paves the way for adaptation strategies that can best address the underlying components of hazard, exposure and vulnerability (Carey et al., 2014; McDowell and Koppes, 2017; Allen et al., 2018; Vaidya et al., 2019). Some degree of adaptation action has been identified in a number of countries with glacier-covered mountain ranges, mostly in the form of reactive responses (rather than formal anticipatory plans) to high-mountain hazards (Xenarios et al., 2018; McDowell et al., 2019) (Figure 2.9). However, scientific literature reflecting on lessons learned from adaptation efforts generally remains scarce. Specifically for flood and landslide hazards, adaptation strategies that were applied include: hard engineering solutions such as lowering of glacier lake levels, channel engineering, or slope stabilisation that reduce the hazard potential; nature-based solutions such as revegetation efforts to stabilise hazard-prone slopes or channels; hazard and risk mapping as a basis for land zoning and early warning systems that reduce potential exposure; various community-level interventions to develop disaster response programmes, build local capacities and reduce vulnerability. For example, there is a long tradition of engineered responses to reduce glacier flood risk, most notably beginning in the mid-20th century in Peru (Box 2.4), Italian and Swiss Alps (Haeberli et al., 2001), and more recently in the Himalaya (Ives et al., 2010). There is no published evidence that avalanche risk management, through defence structures design and norms, control measures and warning systems, has been modified as an adaptation to climate change, over the past decades. Projected changes in avalanche character bear potential reductions of the effectiveness of current approaches for infrastructure design and avalanche risk management (Ancey and Bain, 2015). Early warning systems necessitate strong local engagement and capacity building to ensure communities know how to prepare for and respond to emergencies, and to ensure the long-term sustainability of any such project. In Pakistan and Chile, for instance, glacier flood warnings, evacuation and post-disaster relief have largely been community-led (Ashraf et al., 2012; Anacona et al., 2015). Cutter et al. (2012) highlight the post-recovery and reconstruction period as an opportunity to build new resilience and adaptive capacities. Ziegler et al. (2014) exemplify consequences when such process is rushed or poorly supported by appropriate long-term planning, as illustrated following the 2013 Kedarnath glacier flood disaster, where guest houses and even schools were being rebuilt in the same exposed locations, driven by short-term perspectives. As changes in the mountain cryosphere, together with socio-economic, cultural and political developments are producing conditions beyond historical precedent, related responses are suggested to include forward-thinking planning and anticipation of emerging risks and opportunities (Haeberli et al., 2016). Researchers, policy-makers, international donors and local communities do not always agree on the timing of disaster risk reduction projects and programs, impeding full coordination (Huggel et al., 2015b; Allen et al., 2018). Several authors highlight the value of improved evidential basis to underpin adaptation planning. Thereby, transdisciplinary and cross-regional collaboration that places human societies at the centre of studies provides a basis for more effective and sustainable adaptation strategies (McDowell et al., 2014; Carey et al., 2017; McDowell et al., 2019; Vaidya et al., 2019). In summary, the evidence from regions affected by cryospheric floods, avalanches and landslides generally confirms the findings from the SREX report (Chapter 3), including the requirement for multi-pronged approaches customised to local circumstances, integration of Indigenous Knowledge and Local Knowledge Subject to Copyedit 2-43 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere (Cross-Chapter Box 4 in Chapter 1) together with improved scientific understanding and technical capacities, strong local participation and early engagement in the process, and high-level communication and exchange between all actors. Particularly for mountain regions, there is high confidence that integration of knowledge and practices across natural and social sciences, and the humanities, is most efficient in addressing complex hazards and risks related to glaciers, snow, and permafrost. [START BOX 2.4 HERE] Box 2.4: Challenges to Farmers and Local Population Related to Shrinkages in the Cryosphere: Cordillera Blanca, Peru The Cordillera Blanca of Peru contains most of the glaciers in the tropics, and its glacier coverage declined significantly in the recent past (Burns and Nolin, 2014; Mark et al., 2017). Since the 1940s, glacier hazards have killed thousands (Carey, 2005) and remain threatening. Glacier wastage has also reduced river runoff in most of its basins in recent decades, particularly in the dry season (Baraer et al., 2012; Vuille et al., 2018). Residents living adjacent to the Cordillera Blanca have long recognized this glacier shrinkage, including rural populations living near glaciers and urban residents worried about glacier lake floods and glacier landslides (Jurt et al., 2015; Walter, 2017). Glacier hazards and the glacier runoff variability increase exposure and uncertainty while diminishing adaptive capacity (Rasmussen, 2016). Cordillera Blanca residents’ risk of glacier-related disasters is amplified by intersecting physical and societal factors. Cryosphere hazards include expanding or newly forming glacial lakes, slope instability, and other consequences of rising temperatures, and precipitation changes (Emmer et al., 2016; Colonia et al., 2017; Haeberli et al., 2017). Human vulnerability to these hazards is conditioned by factors such as poverty, limited political influence and resources, minimal access to education and healthcare, and weak government institutions (Hegglin and Huggel, 2008; Carey et al., 2012; Lynch, 2012; Carey et al., 2014; Heikkinen, 2017). Early warning systems have been, or are being, installed at glacial lakes Laguna 513 and Palcacocha to protect populations (Muñoz et al., 2016). Lake 513 was lowered by 20 m for outburst prevention in the early 1990s but nonetheless caused a destructive flood in 2010, though much smaller and less destructive than a flood that would have been expected without previous lake mitigation works (Carey et al., 2012; Schneider et al., 2014). An early warning system was subsequently installed, but some local residents destroyed it in 2017 due to political, social and cultural conflicts (Fraser, 2017). The nearby Lake Palcacocha also threatens populations (Wegner, 2014; Somos-Valenzuela et al., 2016). The usefulness for ground-level education and communication regarding advanced early warning systems has been demonstrated in Penu (Muñoz et al., 2016). Vulnerability to hydrologic variability and declining glacier runoff is also shaped by intertwining human and biophysical drivers playing out in dynamic hydro-social systems (Bury et al., 2013; Rasmussen et al., 2014; Drenkhan et al., 2015; Carey et al., 2017). Water security is influenced by both water availability (supply from glaciers) as well as by water distribution, which is affected by factors such as water laws and policies, global demand for agricultural products grown in the lower Santa River basin, energy demands and hydroelectricity production, potable water usage, and livelihood transformations over time (Carey et al., 2014; Vuille et al., 2018). In some cases, the formation of new glacial lakes can create opportunities as well as hazards, such as new tourist attractions and reservoirs of water, thereby showing how socioeconomic and geophysical forces intersect in complex ways (Colonia et al., 2017). [END BOX 2.4 HERE] Subject to Copyedit 2-44 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Figure 2.8: Observed changes in the cryosphere and impacts on ecosystems, other natural systems and human systems over past decades that can at least partly be attributed to changes in the cryosphere. Only observations documented in the scientific literature are shown, but impacts may also be experienced elsewhere. Shading denotes mountainous areas. Confidence levels (high shown by filled; medium shown by unfilled tetrix boxes) refer to confidence in attribution to cryospheric changes. Figure is based on observed impacts listed in Table SM2.11. 2.3.3 Ecosystems Widespread climate-driven ecological changes have occurred in high-mountain ecosystems over the past century. Those impacts were assessed in a dedicated manner only in earlier IPCC assessments (Beniston and Fox, 1996; Gitay et al., 2001; Fischlin et al., 2007) but not in AR5 (Settele et al., 2014). Two of the most evident changes include range shifts of plants and animals in Central Europe and the Himalaya but also for other mountain regions (e.g., Morueta-Holme et al., 2015; Evangelista et al., 2016; Freeman et al., 2018; Liang et al., 2018; You et al., 2018; He et al., 2019), and increases in species richness on mountain summits (Khamis et al., 2016; Fell et al., 2017; Steinbauer et al., 2018) of which some have accelerated during recent decades (e.g., Steinbauer et al., 2018), though slowing over the past ten years in Austria (e.g., Lamprecht et al., 2018). While many changes in freshwater communities have been directly attributed to changes in the cryosphere (Jacobsen et al., 2012; Milner et al., 2017), separating the direct influence of atmospheric warming from the influence of concomitant cryospheric change and independent biotic processes has been often challenging for terrestrial ecosystems (Grytnes et al., 2014; Lesica and Crone, 2016; Frei et al., 2018; Lamprecht et al., 2018). Changing climate in high mountains places further stress on biota, which are already impacted by land use and its change, direct exploitation, and pollutants (Díaz et al., 2019; Wester et al., 2019). Species are required to shift their behaviors, including seasonal aspects, and distributional ranges to track suitable climate conditions (Settele et al., 2014). In SR1.5, climate change scenarios exceeding mean Subject to Copyedit 2-45 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere global warming of 1.5° C relative to preindustrial levels have been estimated to lead to major impacts on species abundances, community structure, and ecosystem functioning in high-mountain areas (HoeghGuldberg et al., 2018). The size and isolation of mountain habitats (Steinbauer et al., 2016; Cotto et al., 2017), which may vary strongly with the topography of mountain ridges (Elsen and Tingley, 2015; Graae et al., 2018), affects critically the survival of species as they migrate across mountain ranges, increasing in general the risks for many species from climate change (Settele et al., 2014; Dobrowski and Parks, 2016). 2.3.3.1 Terrestrial Biota The cryosphere can play a critical role in moderating and driving how species respond to climate change in high mountains (high confidence). Many mountain plant and animal species have changed abundances and migrated upslope while expanding or contracting their ranges over the past decades to century, whereas others show no change (Morueta-Holme et al., 2015; Suding et al., 2015; Lesica and Crone, 2016; Fadrique et al., 2018; Freeman et al., 2018; Rumpf et al., 2018; Johnston et al., 2019; Rumpf et al., 2019) (medium agreement, robust evidence). These responses are often linked directly to warming, yet a changing cryosphere, e.g. in the form of decreasing snow thickness or altered seasonality of snow (e.g., Matteodo et al., 2016; Kirkpatrick et al., 2017; Amagai et al., 2018; Wu et al., 2018) or indirectly leading to changes in soil moisture (Harpold and Molotch, 2015), can play a significant role for growth, fitness and survival of many species (e.g., Grytnes et al., 2014; Winkler et al., 2016) (medium evidence, high agreement). Cryospheric changes were found to be beneficial for some plant species and for ecosystems in some regions, improving a number of ecosystem services, such as by provisioning new habitat for endemic plant species and increasing plant productivity (high confidence). Decreasing snow-cover duration, glacier retreat and permafrost thaw have already and will over coming decades allow plant species, including some endemic species, to increase their abundance and extend their range in many mountain ranges (Yang et al., 2010a; Grytnes et al., 2014; Elsen and Tingley, 2015; Dolezal et al., 2016; Wang et al., 2016b; D'Amico et al., 2017; Liang et al., 2018; Yang et al., 2018; You et al., 2018; He et al., 2019). Over recent decades, plant colonization after glacier retreat has been swift e.g. at many sites with favorable soils in the European Alps (Matthews and Vater, 2015; Fickert and Grüninger, 2018) or has even accelerated compared to 100 years ago (Fickert et al., 2016). At other sites of the European Alps (D'Amico et al., 2017) and in other mountain ranges (e.g., Andes and Alaska; Darcy et al., 2018; Zimmer et al., 2018) the rate of colonization remains slow due to soil type, soil formation and phosphorous limitation (Darcy et al., 2018). In Bhutan, snowlines have ascended and new plant species have established themselves in these areas, yet despite range expansion and increased productivity, yak herders describe impacts on the ecosystem services as mostly negative (Wangchuk and Wangdi, 2018). Earlier snowmelt often leads to earlier plant growth and, provided there is sufficient water, including from underlying permafrost, plant productivity has increased in many alpine regions (e.g., Williams et al., 2015; Yang et al., 2018). Decreased snow-cover duration has led to colonization of snowbed communities by wide-ranging species in several regions, e.g. Australian Alps (Pickering et al., 2014), though this can lead to declines in the abundance of resident species, e.g. Swiss Alps (Matteodo et al., 2016). Cryospheric change in high mountains directly harms some plant species and ecosystems in some regions, degrading a number of ecosystem services, such as maintaining regional and global biodiversity, and some provisioning services, e.g. fodder or wood production, in terms of timing and magnitude (high confidence). In mountains, microrefugia (a local environment different from surrounding areas) and isolation have contributed to high plant endemism that increases with elevation (Steinbauer et al., 2016; Zhang and Zhang, 2017; Muellner-Riehl, 2019). Microrefugia may enable alpine species to persist if global warming remains below 2°C relative pre-industrial levels (Scherrer and Körner, 2011; Hannah et al., 2014; Graae et al., 2018) (medium evidence, medium agreement). Yet, where glaciers have been retreating over recent decades, cool microrefugia have shifted location or decreased in extent (Gentili et al., 2015). In regions with insufficient summer precipitation, earlier snowmelt and absence of permafrost lead to insufficient water supply during the growing season, and consequently an earlier end of peak season, altered species composition, and a decline in greenness or productivity (Trujillo et al., 2012; Sloat et al., 2015; Williams et al., 2015; Yang et al., 2018) (medium evidence, high agreement). Across elevations, alpine-restricted species show greater sensitivity to the timing of snowmelt than wide-ranging species (Lesica, 2014; Winkler et al., 2018), and though the cause is often not known, some alpine-restricted species have declined in abundance or disappeared in regions with distinctive flora (Evangelista et al., 2016; Giménez-Benavides et al., 2018; Lamprecht et al., 2018; Panetta et al., 2018) (medium evidence, high agreement). Subject to Copyedit 2-46 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere The shrinking cryosphere represents a loss of critical habitat for wildlife that depend on snow and ice cover, affecting well-known and unique high-elevation species (high confidence). Areas with seasonal snow and glaciers are essential habitat for birds and mammals within mountain ecosystems for foraging, relief from climate stress, food caching and nesting grounds (Hall et al., 2016; Rosvold, 2016) (robust evidence). Above 5,000 m a.s.l. in Peru, there was recently a first observation of bird nesting for which its nesting may be glacier obligate (Hardy et al., 2018). The insulated and thermally stable region under the snow at the soilsnow interface, termed the subnivean, has been affected by changing snowpack, limiting winter activity and decreasing population growth for some mountain animals, including frogs, rodents and small carnivores (Penczykowski et al., 2017; Zuckerberg and Pauli, 2018; Kissel et al., 2019) (medium evidence). Many mountain animals have been observed to change their behavior in a subtle manner, e.g. in foraging or hunting behavior, due to cryospheric changes (e.g., Rosvold, 2016; Büntgen et al., 2017; Mahoney et al., 2018) (medium evidence, high agreement). In the Canadian Rocky Mountains, grizzly bear have moved to new snow-free habitat after emerging in spring from hibernation to dig for forage, which may increase the risk of human-bear encounters (Berman et al., 2019). In the U.S. Central Rocky Mountains, migratory herbivores, such as elk, moose and bison, track newly emergent vegetation that greens soon after snowmelt (Merkle et al., 2016). For elk this was found to increase fat gain (Middleton et al., 2018). Due to loss of snow patches that increase surface water and thus insect abundance, some mammal species, e.g. reindeer and ibex, have changed their foraging behavior to evade the biting insects with negative impacts on reproductive fitness (Vors and Boyce, 2009; Büntgen et al., 2017). Many endemic plant and animal species including mammals and invertebrates in high-mountain regions are vulnerable to further decreasing snow-cover duration, i.e. later onset of snow accumulation and/or earlier snowmelt (high confidence) (Williams et al., 2015; Slatyer et al., 2017). Winter-white animals for which coat or plumage color is cued by day length will confront more days with brown snowless ground, which has already contributed to range contractions for several species, including hares and ptarmigan (Imperio et al., 2013; Sultaire et al., 2016; Pedersen et al., 2017) (robust evidence). Under all climate scenarios, the duration of this camouflage mismatch will increase, enhancing predation rates thereby decreasing populations of coatcolor changing species (e.g., 24% decrease by late century under RCP 8.5 for snowshoe hares; Zimova et al., 2016; see also Atmeh et al., 2018; Wilson, 2018) (medium evidence, high agreement). For roe deer (Plard et al., 2014) and mountain goats (White et al., 2017), climate-driven changes in snowmelt duration and summer temperatures will reduce survival considerably under RCP 4.5 and 8.5 scenarios (medium evidence, high agreement). 2.3.3.2 Freshwater Biota Biota in mountain freshwater ecosystems is affected by cryospheric change through alterations in both the quantity and timing of runoff from glaciers and snowmelt. Where melt water from glaciers decreases, river flows have become more variable, with water temperature and overall channel stability increasing and habitats becoming less complex (Giersch et al., 2017; Milner et al., 2017) (medium evidence, medium agreement). Analysis of three invertebrate datasets from tropical (Ecuador), temperate (Italian Alps) and sub-Arctic (Iceland) alpine regions indicates that a number of cold-adapted species have decreased in abundance below a threshold of watershed glacier cover varying from 19–32%. With complete loss of the glaciers 11–38% of the regional species will be lost (Jacobsen et al., 2012; Milner et al., 2017) (medium confidence). As evidenced in Europe (Pyrenees, Italian Alps) and North America (Rocky Mountains) (Brown et al., 2007; Giersch et al., 2015; Giersch et al., 2017; Lencioni, 2018) the loss of these invertebrates, many of them endemic, as glacier runoff decreases and transitions to a regime more dominated by snowmelt leading to a reduction in turnover between and within stream reaches (beta diversity) and regional (gamma) diversity (very high confidence). Regional genetic diversity within individual riverine invertebrate species in mountain headwater areas has decreased with the loss of environmental heterogeneity (Giersch et al., 2017), as decreasing glacier runoff reduces the isolation of individuals permitting a greater degree of genetic intermixing (Finn et al., 2013; Finn et al., 2016; Jordan et al., 2016; Hotaling et al., 2018) (medium evidence, high agreement). However, local (alpha) diversity, dominated by generalist species of invertebrates and algae, has increased (Khamis et al., 2016; Fell et al., 2017; Brown et al., 2018) (very high confidence) in Subject to Copyedit 2-47 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere certain regions as species move upstream, although not in the Andes, where downstream migration has been observed (Jacobsen et al., 2014; Cauvy-Fraunié et al., 2016). Many climate variables influence fisheries, through both direct and indirect pathways. The key variables linked to cryospheric change include: changes in air and water temperature, precipitation, nutrient levels and ice cover (Stenseth et al., 2003). A shrinking cryosphere has significantly affected cold mountain resident salmonids (e.g., brook trout, Salvelinus fontinalis), causing further migration upstream in summer thereby shrinking their range (Hari et al., 2006; Eby et al., 2014; Young et al., 2018). Within the Yanamarey watershed of the Cordillera Blanca in Peru, fish stocks have either declined markedly or have become extinct in many streams, possibly due to seasonal reductions of fish habitat in the upper watershed resulting from glacier recession (Bury et al., 2011; Vuille et al., 2018). In contrast, glacier recession in the mountains of coastal Alaska and to a lesser extent the Pacific Northwest have created a large number of new stream systems that have been, and could continue to be with further glacier retreat, colonized from the sea by salmon species that contribute to both commercial and sport fisheries (Milner et al., 2017; Schoen et al., 2017) (medium confidence). Changes in water temperature will vary seasonally, and a potential decreased frequency of rain-on-snow events in winter compared to rain-on-ground would increase water temperature, benefiting overwintering survival (Leach and Moore, 2014). Increased water temperature remaining below thermal tolerance limits for fish and occurring earlier in the year can benefit overall fish growth and increase fitness (Comola et al., 2015) (medium evidence, medium agreement). In the future, increased primary production dominated by diatoms and golden algae will occur in streams as glacier runoff decreases, although some cold-tolerant diatom species will be lost, resulting in a decrease in regional diversity (Fell et al., 2017; Fell et al., 2018). Reduced glacier runoff is projected to improve water clarity in many mountain lakes, increasing biotic diversity and the abundance of bacterial and algal communities and thus primary production (Peter and Sommaruga, 2016) (limited evidence). Extinction of range-restricted prey species may increase as more favourable conditions facilitate the upstream movement of large-bodied invertebrate predators (Khamis et al., 2015) (medium confidence). Modelling studies indicate a reduction in the range of native species, notably trout, in mountain streams, (Papadaki et al., 2016; Vigano et al., 2016; Young et al., 2018) (medium evidence, high agreement), which will potentially impact sport fisheries. In Northwest North America, where salmon are important in native subsistence as well as commercial and sport fisheries, all species will potentially be affected by reductions in glacial runoff from mountain glaciers over time (Milner et al., 2017; Schoen et al., 2017), particularly in larger systems where migratory corridors to spawning grounds are reduced (medium confidence). In summary, cryospheric change will alter freshwater communities with increases in local biodiversity but range shrinkage and extinctions for some species causes regional biodiversity to decrease (robust evidence, medium agreement, i.e. high confidence). 2.3.3.3 Ecosystem Services and Adaptation The trend to a higher productivity in high-mountain ecosystems due to a warmer environment and cryospheric changes, affects provisioning and regulating services (high confidence). Due to earlier snowmelt, the growing season has begun earlier, e.g. on the Tibetan Plateau, and in the Swiss Alps (Wang et al., 2017; Xie et al., 2018), and in some regions earlier growth has been linked to greater plant production or greater net ecosystem production, i.e. carbon uptake (Scholz et al., 2018; Wang et al., 2018; Wu et al., 2018). In other areas productivity has decreased, despite a longer growing season, e.g. in U.S. Rocky Mountains, U.S. Sierra Nevada Mountains, Swiss Alps, and Tibetan Plateau (Arnold et al., 2014; Sloat et al., 2015; Wang et al., 2017; De Boeck et al., 2018; Knowles et al., 2018) (robust evidence, medium agreement). Changed productivity of the vegetation in turn can affect the timing, quantity and quality of water supply, a critical regulating service ecosystems play in high mountain areas (Goulden and Bales, 2014; Hubbard et al., 2018) (medium confidence). Permafrost degradation has dramatically changed some alpine ecosystems through altered soil temperature and permeability, decreasing the climate regulating service of a vast region and leading to lowered ground water and new and shrinking lakes on the Tibetan Plateau (Jin et al., 2009; Yang et al., 2010b; Shen et al., 2018) (medium evidence, high agreement). Ecosystems and their services are vulnerable to changes in the intensity and/or the frequency of a disturbance regime that exceed the previous range of variation (Johnstone et al., 2016; Camac et al., 2017; Fairman et al., Subject to Copyedit 2-48 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere 2017); cf. 3.4.3.2 Ecosystems and their Services) (high confidence). For example for fire in the Western USA, mountain ecosystems are experiencing an increase in the number and extent of wildfires, which have been attributed to many factors including climate factors such as earlier snowmelt and vapor-pressure deficit (Settele et al., 2014; Westerling, 2016; Kitzberger et al., 2017; Littell, 2018; Littell et al., 2018). Similarly, landslides and floods in many areas have been attributed to cryospheric changes (Section 2.3.2). Disturbances can feedback and diminish many of the ecosystem services such as provisioning, regulating, and cultural services (Millar and Stephenson, 2015; McDowell and Koppes, 2017; Mcdowell et al., 2018; Murphy et al., 2018; Maxwell et al., 2019). , Consistent with AR5 findings (Settele et al., 2014) the capacity of many freshwater and terrestrial mountain species to adapt naturally to climate change is projected to be exceeded for high warming levels, leading to species migration across mountain ranges or loss with consequences for many ecosystem services (Elsen and Tingley, 2015; Dobrowski and Parks, 2016; Pecl et al., 2017; Rumpf et al., 2019) (robust evidence, medium agreement, i.e. high confidence). Although the adaptive potential of aquatic biota to projected changes in glacial runoff is not fully understood (Lencioni et al., 2015), dispersion and phenotypic plasticity together with additional microrefugia formation due to cryospheric changes, is expected to help threatened species to better adapt, perhaps even in the long term (Shama and Robinson, 2009). Likewise, traits shaped by climate and with high genetically-based standing variation may be used to spatially identify, map, and manage global “hotspots” for evolutionary rescue from climate change (Jones et al., 2018; Mills et al., 2018). Nature conservation increases the potential for mitigating adverse effects on many of these ecosystem services, including those that are essential for the support of the livelihoods and the culture of mountain peoples, including economical aspects such as recreation and tourism (e.g., Palomo, 2017; Elsen et al., 2018; Wester et al., 2019) (medium confidence). 2.3.4 Infrastructure and Mining There is high confidence that permafrost thaw has had negative impacts on the integrity of infrastructure in high-mountain areas. Like in polar regions (Section 3.4.3.3.4), the local effects of infrastructure together with climate change degraded permafrost beneath and around structures (Dall’Amico et al., 2011; Doré et al., 2016) Infrastructure on permafrost in the European Alps, mostly found near mountain summits but not in major valleys, has been destabilised by permafrost thaw, including mountain stations in France and Austria (Ravanel et al., 2013; Keuschnig et al., 2015; Duvillard et al., 2019) as well as avalanche defence structures (Phillips and Margreth, 2008) and a ski lift (Phillips and Morrow, 2007) in Switzerland. On the Tibet Plateau, deformation or damage has been found on roads (Yu et al., 2013; Chai et al., 2018), power transmission infrastructure (Guo et al., 2016) and around an oil pipeline (Yu et al., 2016). For infrastructure on permafrost, engineering practices suitable for polar and high-mountain environments (Doré et al., 2016) as well as specific for steep terrain (Bommer et al., 2010) have been developed to support adaptation. In some mountain regions, glacier retreat and related processes of change in the cryosphere have afforded greater accessibility for extractive industries and related activities to mine minerals and metals (medium confidence). Accelerated glacier shrinkage and retreat have been reported to facilitate mining activities in Chile, Argentina and Peru (Brenning, 2008; Brenning and Azócar, 2010; Anacona et al., 2018) and Kyrgyzstan (Kronenberg, 2013; Petrakov et al., 2016), which also interact with and have consequences for other social, cultural, economic, political, and legal measures, where climate change impacts also play a role (Brenning and Azócar, 2010; Evans et al., 2016; Khadim, 2016; Anacona et al., 2018). However, negative impacts due to cryosphere changes may also occur. One study projects that reductions in glacier meltwater and snowmelt in the watershed in the Chilean Andes will lead to a reduction of water supply to a copper mine by 2075–2100 of 28% under scenario A2 and of 6% under B2; construction of infrastructure to draw water from other sources will cost between US$ 16–137 million (Correa-Ibanez et al., 2018). Conversely, there is also evidence suggesting that some of these mining activities affect glaciers locally, and the mountain environment around them, further altering glacier dynamics, glacier structure and permafrost degradation, due mainly to excavation, extraction, and use of explosives (Brenning, 2008; Brenning and Azócar, 2010; Kronenberg, 2013), and deposition of dust and other mine waste material close to or top of glaciers during extraction and transportation (Brenning, 2008; Torgoev and Omorov, 2014; Arenson et al., 2015b; Jamieson et al., 2015). These activities have reportedly generated slope instabilities (Brenning, 2008; Brenning and Azócar, 2010; Torgoev and Omorov, 2014), glacier mass loss due to enhanced surface melt from dust and debris deposition (Torgoev and Omorov, 2014; Arenson et al., 2015b; Petrakov et al., 2016), and even glacier advance by several kilometres (Jamieson et al., 2015), although their impact is considered Subject to Copyedit 2-49 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere less than that reported for changes in glaciers due to climatic change (limited evidence, medium agreement). Glacier Protection Laws and similar measures have been introduced in countries such as Chile and Argentina to address these impacts (Khadim, 2016; Anacona et al., 2018; Navarro et al., 2018). In addition, the United Nations Human Rights Council passed a declaration in 2018 to “protect and restore water-related ecosystems” in mountain areas as elsewhere from contamination by mining (UNHRC, 2018); however, evidence on the effectiveness of these measures remains inconclusive. 2.3.5 Tourism and Recreation The mountain cryosphere provides important aesthetic, cultural, and recreational services to society (Xiao et al., 2015). These services support tourism, providing economic contributions and livelihood options to mountain communities and beyond. The relevant changes in the cryosphere affecting mountain tourism and recreation include shorter seasons of snow cover, more winter precipitation falling as rain instead of snow, and declining glaciers and permafrost (Sections 2.2.1, 2.2.2 and 2.2.3). Downhill skiing, the most popular form of snow recreation, occurs in 67 countries (Vanat, 2018). The Alps in Europe support the largest ski industry (Vanat, 2018). In Europe, the growth of alpine skiing and winter tourism after 1930 brought major economic growth to alpine regions and transformed winter sports into a multi-billion USD industry (Denning, 2014). Sixteen percent of skier visits occur in the USA, where expenditures from all recreational snow sports generated more than 695,000 jobs and 72.7 billion USD in trip-related spending in 2016 (Outdoor Industry Association, 2017). While the number of ski resorts in the USA has been decreasing since the 1980s, China added 57 new ski resorts in 2017 (Vanat, 2018). Although the bulk of economic activity is held within mountain communities, supply chains for production of ski equipment and apparel span the globe. Steiger et al. (2017) point out that Asia, Africa and South America are underrepresented in the ski tourism literature, and Africa and the Middle East are not significant markets from a ski tourism perspective. Skiing’s reliance on favourable atmospheric and snow conditions make it particularly vulnerable to climate change (Arent et al., 2014; Hoegh-Guldberg et al., 2018). Snow reliability, although not universally defined, quantifies whether the snow cover is sufficient for ski resorts operations. Depending on the context, it focuses on specific periods of the winter season, and may account for interannual variability and/or for snow management (Steiger et al., 2017). The effects of less snow, due to strong correlation between snow cover and skier visits, cost the economy of the USA 1 billion USD and 17,400 jobs per year between 2001 and 2016 in years of less seasonal snow (Hagenstad et al., 2018). Efforts to reduce climate change impacts and risks to economic losses focus on increased snowmaking, i.e., artificial production of snow (Steiger et al., 2017), summertime slope preparation (Pintaldi et al., 2017), grooming (Steiger et al., 2017), and snow farming, i.e. storage of snow (Grünewald et al., 2018). The effectiveness of snow management methods as adaptation to long-term climate change depends on sufficiently low air temperature conditions needed for snowmaking, water and energy availability, compliance with environmental regulations (de Jong, 2015), and ability to pay for investment and operating costs. When these requirements are met, evidence over the past decades shows that snow management methods have generally proven efficient in reducing the impact of reduced natural snow cover duration for many resorts (Dawson and Scott, 2013; Hopkins and Maclean, 2014; Steiger et al., 2017; Spandre et al., 2019a). The number of skier visits was found to be 39% less sensitive to natural snow variations in Swiss ski resorts with 30% areal snowmaking coverage (representing the national average), compared to resorts without snowmaking (Gonseth, 2013). In some regions, many resorts (mostly smaller, low-elevation resorts) have closed due to unfavourable snow conditions brought on by climate change and/or the associated need for large capital investments for snowmaking capacities (e.g., in north-eastern USA; Beaudin and Huang, 2014)). To offset loss in ski tourism revenue, a key adaptation strategy is diversification, offering other non-snow recreation options such as mountain biking, mountain coasters and alpine slides, indoor climbing walls and water parks, festivals and other special events (Figure 2.9; Hagenstad et al., 2018; Da Silva et al., 2019). In the near term (2031–2050) and regardless of the greenhouse gas emission scenario, risks to snow reliability exist for many resorts, especially at lower elevation, although snow reliability is projected to be maintained at many resorts in North America (Wobus et al., 2017) and in the European Alps, Pyrenees and in Scandinavia (Marke et al., 2015; Steiger et al., 2017; Scott et al., 2019; Spandre et al., 2019a; Spandre et al., 2019b). At the end of the century (2081–2100), under RCP8.5 snow reliability is projected to be unviable for most ski resorts under current operating practices in North America, the European Alps and Pyrenees, Scandinavia and Japan, with some exceptions at high elevation or high latitudes (Steiger et al., 2017; Wobus Subject to Copyedit 2-50 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere et al., 2017; Suzuki-Parker et al., 2018; Scott et al., 2019; Spandre et al., 2019a; Spandre et al., 2019b). Only few studies have used RCP2.6 in the context of ski tourism, and results indicate that the risks at the end of the century (2081–2100) are expected to be similar to the near term impacts (2031–2050) (Scott et al., 2019; Spandre et al., 2019a). The projected economic losses reported in the literature include an annual loss in hotel revenues of 560 million Euro (2012 value) in Europe, compared to the period 1971–2000 under a 2°C global warming scenario (Damm et al., 2017). This estimate includes population projections but does not account for snow management. In the USA, Wobus et al. (2017) estimate annual revenue losses from tickets (skiing) and day fees (cross country skiing and snowmobiling) due to reduced snow season length, range from 340 to 780 million USD in 2050 for RCP4.5 and RCP8.5, respectively, and from 130 million USD to 2 billion USD in 2090 for RCP4.5 and RCP8.5, respectively, taking into account snow management and population projections. Total economic losses from these studies would be much higher if all costs were included (costs for tickets, transport, lodging, food, and equipment). Regardless of the climate scenario, as risk of financial unviability increases, there are reported expectations that companies would need to forecast when their assets may become stranded assets and require devaluation or conversion to liabilities, and report this on their balance sheets (Caldecott et al., 2016). Economic impacts are projected to occur in other snow-based winter activities including events (e.g., ski races) and other recreation activities such as cross-country skiing, snowshoeing, backcountry skiing, ice climbing, sledding, snowmobiling and snow tubing. By 2050, 13 (out of 21) prior Olympic Winter Games locations are projected to exhibit adequate snow reliability under RCP2.6, and 10 under RCP8.5. By 2080, the number decreases to 12 and 8, respectively (Scott et al., 2018). Even for cities remaining cold enough to host ski competitions, costs are projected to rise for making and stockpiling snow, as was the case in Sochi, Russia, 2014 and Vancouver, Canada, 2010 (Scott et al., 2018), and preserving race courses such as salting (Hagenstad et al., 2018). In summer, cryosphere changes are impacting glacier-related activities (hiking, sightseeing, skiing and climbing and mountaineering) (Figure 2.8). In recent years, several ski resorts operating on glaciers have ceased summer operations due to unfavourable snow conditions and excessive operating costs (e.g., Falk, 2016). Snow management and snowmaking are increasingly used on glaciers (Fischer et al., 2016). Glacier retreat has led to increased moraine instability which can compromise hiker and climber safety along established trails and common access routes, e.g. in Iceland (Welling et al., 2019), though it has made some areas in the Peruvian Andes more accessible to trekkers (Vuille et al., 2018). In response, some hiking routes have been adjusted and ladders and fixed anchors installed, (Duvillard et al., 2015; Mourey and Ravanel, 2017). As permafrost thaws, rock falls on and off glaciers are increasingly observed, threatening the safety of hikers and mountaineers, e.g. in Switzerland (Temme, 2015) and New Zealand (Purdie et al., 2015). Glacier retreat and permafrost thaw have induced major changes to iconic mountaineering routes in the Mont-Blanc area with impacts on mountaineering practices, such as shifts in suitable climbing seasons, and reduced route safety (Mourey and Ravanel, 2017; Mourey et al., 2019). Cryosphere decline has also reduced opportunities for ice-climbing and reduced attractions for summer trekking in the Cascade Mountains, USA (Orlove et al., 2019). In response to these impacts, tour companies have shifted to new sites, diversified to offer other activities or simply reduced their activities (Furunes and Mykletun, 2012) (Figure 2.9). Steps to improve consultation and participatory approaches to understand risk perception and design joint action between affected communities, authorities and operators, are evident, e.g. in Iceland (Welling et al., 2019). In some cases, new opportunities are presented such as marketing “climate change tourism” where visitors are attracted by ‘last chance’ opportunities to view a glacier; e.g. in New Zealand (Stewart et al., 2016), in China (Wang et al., 2010) or through changing landscapes such as new lakes, for instance in Iceland (Þórhallsdóttir and Ólafsson, 2017) or to view the loss of a glacier, e.g. in the Bolivian Andes (Kaenzig et al., 2016). The opening of a trekking route promoting this opportunity created tensions between a National Park and a local indigenous community in the Peruvian Andes over the management and allocation of revenue from the route (Rasmussen, 2019). The consequences of ongoing and future glacier retreat are projected to negatively impact trekking and mountaineering in the Himalaya (Watson and King, 2018). Reduced snow cover has also negatively impacted trekking in the Himalaya, since tourists find the mountains less attractive as a destination, and the reduced water availability affects the ability of hotels and campsites to serve visitors (Becken et al., 2013). In summary, financial risks to mountain communities that depend on tourism for income, are high and include losses to revenues generated from recreation primarily in the winter season. Adaptation to Subject to Copyedit 2-51 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere cryosphere change for ski tourism focuses on snowmaking and is expected to be moderately effective for many locations in the near term (2031–2050), but it is unlikely to substantially reduce the risks in most locations in the longer term (end of century) (high confidence). Determining the extent to which glacier retreat and permafrost thaw impact upon overall visitor numbers in summer tourism, and how any losses or increased costs are offset by opportunities, is inconclusive. Furthermore, tourism is also impacted by cryospheric change that impacts on water resources availability, increasing competition for its use (Section 2.3.1.3). Figure 2.9: a) Documented number of individual adaptation actions distributed across seven of the high-mountain regions addressed in this Chapter, with pie charts indicating the number of adaptation measures for sectors addressed in this chapter (left pie chart), and the relative proportion of these classified as either ‘formal’, ‘autonomous’ or ‘undefined’ (right pie chart). Note that for regions with less than 5 reported adaptation measures were excluded from the figure (i.e. Caucasus, Iceland and Alaska), however these are detailed in Table SM2.9. b) Number of publications reported in the assessed literature over time. In some cases, multiple adaptation measures are discussed in a single publication (Table SM2.9). 2.3.6 Cultural Values and Human Well-being Cryosphere changes also impact cultural values, which are held by populations in high mountains and other regions around the world; these impacts often harm human well-being (Tschakert et al., 2019) (medium evidence, high agreement). Cultural values were covered extensively in AR5, with particular emphasis on small island states and the Arctic; the research on cultural values in high-mountain regions is relatively new. Out of a total of 247 UNESCO World Heritage natural sites recognized for their outstanding universal value, 46 sites include glaciers within their boundaries, where the presence of glaciers is stated among the principal reason (5 sites), or secondary reason (28 sites), for World Heritage inscription; complete glacier extinction is Subject to Copyedit 2-52 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere projected by 2100 in 8 to 21 of these sites, under RCP2.6 and RCP8.5 scenarios, respectively, compromising the outstanding universal value placed on these sites, which have been inscribed at least partly for their exceptional glaciers (Bosson et al., 2019). UNESCO defines “outstanding universal value” as “cultural and/or natural significance which is so exceptional as to transcend national boundaries and to be of common importance for present and future generations of all humanity” (UNESCO, 2012). Furthermore, in recognising the importance of the cultural and intangible value placed by communities on aspects of their surrounding environment, such as those afforded by crysosphere elements in the high mountains, are mentioned under the workplan of the Warsaw International Mechanism as a specific work area under ‘Noneconomic loss and damage’ (UNFCCC Secretariat, 2014; Serdeczny, 2019). Cultural values include spiritual, intrinsic and existence values, as well as aesthetic dimensions, which are also an element of tourism and recreation (Section 2.3.6), though they focus more directly on ties to sacred beings or to inherent rights of entities to exist. However, these values overlap, since the visual appeal of natural landscapes links with a sense of the immensity of mountain landscapes, glaciers and fresh snow (Paden et al., 2013; Gagné et al., 2014). Moreover, different stakeholders, such as local communities, tourists and policy-makers, may place different emphasis on specific cultural values (Schirpke et al., 2016). For the indigenous Manangi community of the Annapurna Conservation Area of Nepal, the loss of glaciers which they have observed threatens their ethnic identity (Konchar et al., 2015). Villagers in the Italian Alps also report that glacier retreat weakens their identity (Jurt et al., 2015). Spiritual and intrinsic values in high-mountain regions often, but not exclusively, rest on deeply-held religious beliefs and other local customs (medium evidence, high agreement). Some communities understand mountains through a religious framework (Bernbaum, 2006). In settings as diverse as the Peruvian Andes, the Nepal Himalaya, the Alps, the North Cascades (US), Mount Kilimanjaro and the Hengduan Mountains of southwest China, local populations view glacier retreat as the product of their failure to show respect to sacred beings or to follow proper conduct. Experiencing deep concern that they have disturbed cosmic order, they seek to behave in closer accord with established traditions; they anticipate that the retreat will continue, leading to further environmental degradation and to the decline of natural and social orders—a prospect which causes them distress (Becken et al., 2013; Gagné et al., 2014; Allison, 2015). In the USA, the snowcovered peaks of the Cascades have also evoked a deep sense of awe and majesty, and an obligation to protect them (Carroll, 2012; Duntley, 2015). Similar views are found in the Italian Alps, where villagers speak of treating glacier peaks with “respect,” and state that glacier retreat is due, at least in part, to humans “disturbing” the glaciers (Brugger et al., 2013), resulting in an emotion which Albrecht et al. (2007) termed solastalgia, a kind of deep environmental distress or ecological grief (Cunsolo and Ellis, 2018). Glacier retreat threatens the Indigenous Knowledge and Local Knowledge of populations in mountain regions; this knowledge constitutes a cultural service to wider society by contributing to scientific understanding of glaciers (Cross-Chapter Box 4 in Chapter 1). Though this knowledge is dynamic, and records previous states of glaciers, it has been undermined by the complete disappearance of glaciers in a local area (Rhoades et al., 2008). This knowledge of glaciers is often tied to religious beliefs and practices. It is based on direct observation, stories passed down from one generation to another within community, placenames, locations of structures and other sources (Gagné et al., 2014). Residents of mountain areas can provide dates for previous locations of glacier fronts, sometimes documenting these locations through the presence of structures (Brugger et al., 2013). Much like other cases of data from citizen science (Theobald et al., 2015), their observations often overlap with the record of instrumental observations (Deng et al., 2012), and can significantly extend this record (Mark et al., 2010). An additional cultural value is the contribution of glaciers to the understanding of human history. Glacier retreat has supported the increase of knowledge of past societies by providing access to archaeological materials and other cultural resources that had previously been covered by ice. The discovery of Oetzi, a mummified Bronze Age man whose remains were discovered in 1991 in the Alps near the Italian-Austrian border, marked the beginning of scientific research with such materials (Putzer and Festi, 2014). Subsequent papers described objects that were uncovered in retreating glaciers and shrinking ice patches in the Wrangell-Saint Elias Range (Dixon et al., 2005), the Rocky Mountains (Lee, 2012) and Norway (Bjørgo et al., 2016). This field provides new insight into human cultural history and contributes to global awareness of climate change (Dixon et al., 2014). Though climate change permits the discovery of new artefacts and sites, Subject to Copyedit 2-53 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere it also threatens these objects and places, since they become newly exposed to harsh weather (Callanan, 2016). 2.3.7 Migration, Habitability and Livelihoods High-mountain communities have historically included mobility in their sets of livelihood strategies, as a means to gain access to production zones at different elevations within mountain zones and in lowland areas, and as a response to the strong seasonality of agricultural and pastoral livelihoods. Cryosphere changes in high-mountain areas have influenced human mobility and migration during this century by altering water availability and increasing exposure to mass movements and floods and other cryospheric induced disasters (Figure 2.7) (Barnett et al., 2005; Carey et al., 2017; Rasul and Molden, 2019). These changes affect three forms of human mobility: transhumant pastoralism, temporary or permanent wage labour migration, and displacement, in which entire communities resettle in new areas. Transhumant pastoralism, involving movements between summer and winter pastures, is a centuries-old practice in high-mountain areas (Lozny, 2013). In High Mountain Asia and other regions, it is declining, due to climatic factors, including changes in snow distribution and glaciers, and to non-climatic factors, and is projected to continue declining, at least in the short term (medium evidence, high agreement). The changes in snow and glaciers adversely affect herders at their summer residences and winter camps in the Himalaya (Namgay et al., 2014) and in Scandinavian mountains (Mallory and Boyce, 2018). Reduced winter snowfall has led to poorer pasture quality in Nepal (Gentle and Maraseni, 2012) and India (Ingty, 2017). Other climate change impacts, including erratic snowfall patterns and a decrease in rainfall, are perceived by herders in Afghanistan, Nepal and Pakistan to have resulted in vegetation of lower quality and quantity (Shaoliang et al., 2012; Joshi et al., 2013; Gentle and Thwaites, 2016). Heavy snowfall incidents in winter caused deaths of a large number of livestock in northern Pakistan in 2009 (Shaoliang et al., 2012). Herders in Nepal reported of water scarcity in traditional water sources along migration routes (Gentle and Thwaites, 2016). Increased glacier meltwater has caused lakes on the Tibet Plateau to increase in size, covering pasture areas and leading pastoralists to alter their patterns of seasonal movement (Nyima and Hopping, 2019). However, rising temperatures, with associated effects on snow cover, have some positive impacts. Seasonal migration from winter to summer pastures start earlier in northern Pakistan, and residence in summer pasture lasts longer (Joshi et al., 2013), as it does in Afghanistan (Shaoliang et al., 2012). Wage labour migration is also a centuries-old practice in the Himalaya, the Andes and the European Alps (Macfarlane, 1976; Cole, 1985; Viazzo, 1989). Studies show that migration is a second-order effect of cryosphere changes, since the first-order effects, a decrease in agricultural production (Section 2.3.1.3.1), have led in a number of regions to increased wage labour migration to provide supplementary income (medium evidence, high agreement). Wage labour migration linked to cryosphere changes occurs on several time scales, including short-term, long-term and permanent migration, and on different spatial scales; though migration usually takes place within the country of origin, and sometimes within the region; cases of international migration have also been recorded (Merrey et al., 2018). The studies since AR5 on migration driven by cryosphere changes are concentrated in High Mountain Asia and the Andes, supporting the finding, reported in AR5 Working Group II (Section 12.7), that stress on livelihoods is an important driver of climate change induced migration. The research on such migration also supports the finding in SR15 (Section 4.3.5.6) that migration can have mixed outcomes on reducing socio-economic vulnerability, since cases of increase and of reduction of vulnerability are both found in migration from high-mountain regions that is driven by cryosphere changes. Changing water availability, mass movements and floods are cryosphere processes which drive wage labour migration (medium evidence, high agreement). A debris flow in central Nepal in 2014, in a region where landslides have increased in recent decades, led more than half the households to migrate for months (van der Geest and Schindler, 2016). In the Santa River drainage, Peru, rural populations have declined 10% between 1970 and 2000, and the area of several major subsistence crops also declined (Bury et al., 2013). Research in this region suggests that seasonal wage labour migration from small basins within the main Santa basin is largest in the small drainages in which glacier retreat has reduced meltwater flow most significantly; where this process is not as acute, and streamflow is less reduced, migration rates are lower (Wrathall et al., 2014). A study from a region in the central Peruvian Andes shows that the residents of the villages that have the highest dependence on glacier meltwater travel further and stay away longer than the Subject to Copyedit 2-54 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere residents of the villages where glacier meltwater forms a smaller portion of stream flow (Milan and Ho, 2014). However, the inverse relation between reliance on cryosphere-related water sources and migration was noted in a case in the Naryn River drainage in Kyrgyzstan, where the villages that are more dependent on glacier meltwater had lower, rather than higher, rates of wage labour migration than the villages which were less dependent on it; the villages with lower rates of such migration also had more efficient water management institutions than the others (Hill et al., 2017). Several studies, which project cryosphere-related emigration to continue in the short term, emphasize decreased water availability, due to glacier retreat as a driver in Kyrgyzstan (Chandonnet et al., 2016) and Peru (Oliver-Smith, 2014), and to reduced snow cover in Nepal (Prasain, 2018). In most cases, climate is only one of several drivers (employment opportunities and better educational and health services in lowland areas are others). Several studies show that wage labour migration is more frequent among young adults than among other age groups, supporting the observation in AR5 that climate change migrants worldwide are concentrated in this age (limited evidence, high agreement). This age-specific pattern is found in a valley in northern Pakistan in which agriculture relies on glacier meltwater for irrigation; as river flow decreases, the returns to agricultural labour have declined, and emigration has increased, particularly among the youth, who are assigned, by local cultural practices, to carry out the heaviest work (Parveen et al., 2015). Emigration has increased in recent decades from two valleys in highland Bolivia which rely on glacier meltwater, as water supplies have declined, though other factors also contribute to emigration, including land fragmentation, increasing household needs for income, the lack of local wage-labour opportunities and an interest among the young in educational opportunities located in cities (Brandt et al., 2016). In Nepal, young members of high-elevation pastoral households impacted by cryosphere change have been increasingly engaged in tourism and labour migration since 2000 (Shaoliang et al., 2012); similar responses are reported for Sikkim in the Indian Himalaya (Ingty, 2017). A recent study documents the inter-generational dynamics of emigration from a livestock-raising community in the Peruvian Andes, where glacier retreat has led to reduced streamflow that support crucial dry-season pasture (Alata et al., 2018). Though people 50 years old or older in this community are accustomed to living in the high pasture zones, younger people use livestock-raising as a means of accumulating capital. They sell off their animals and move to towns at lower elevations. This loss of young adults has reduced the capacity of households to undertake the most demanding tasks, particularly in periods of inclement weather, accelerating the decline of herding. As a result, the human and animal populations of the communities are shrinking. Recent research on cryosphere-driven migration shows some cases of complex livelihood interactions or feedback loops, in which migration is not merely a result of changes in agricultural livelihoods, but also has impacts, either positive or negative, on these livelihoods (medium confidence). In some instances, the different livelihood strategies complement each other to support income and well-being. A review of migration in the Himalaya and Hindu Kush found that households that participated in labour migration and received remittances had improved adaptive capacity, and lowered exposure to natural hazards (Banerjee et al., 2018). In other cases, the households and communities, which undertake wage labour migration, encounter conflicts or incompatibilities between migration and agricultural livelihoods. Sustainable management of land, water and other resources is highly labour intensive, and hence labour mobility constrains and limits the adoption of sustainable practices (Gilles et al., 2013). Moreover, the labour available to a household is differentiated by age. In northern Pakistan, where cryosphere changes are reducing streamflow the emigration of young people has led to a decline not only in the labour in fields and orchards, but also a decline in the maintenance of irrigation infrastructure, leading to an overall reduction of the agricultural livelihoods in the community (Parveen et al., 2015). In addition to affecting pastoral transhumance and increasing wage labour migration, cryosphere changes impact human mobility by creating cases of displacement. These cases differ from wage labour migration because they involve entire communities. As a result, they are irreversible, unlike cases in which individuals undertake long-term or permanent migration from their communities but retain the possibility of returning, because, for example, some relatives or former neighbours have remained in place. In this way, these cases of displacement represent cryosphere-driven challenges to habitability. Though natural hazards have historically led some communities to relocate (Section 2.3.2.1.4, Box 2.4), cryosphere changes have contributed to instances of displacement. Unreliable water availability and increased risks of natural hazards are responsible for resettlement of villages in certain high-mountain areas (McDonald, 1989; Parveen et al., 2015). A village in western Nepal moved to lower elevation after decreasing snowfall reduced the flow of Subject to Copyedit 2-55 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere water in the river on which their pastoralism and agriculture depended (Barnett et al., 2005). Three villages in Nepal faced severe declines in agricultural and pastoral livelihoods because decreased snow cover led to reduced soil moisture and to the drying up of springs, which were the historical source of irrigation water; in conjunction with an international non-governmental organisation (INGO), the residents planned a move to a lower area (Prasain, 2018). The issue of habitability arises in the cases, mentioned above, of communities that relocate after floods or debris flows destroy houses and irrigation infrastructure, or damage fields and pastures. It occurs as well in the cases of households with extensive long-term migration, where agricultural and pastoral livelihoods are undermined by reduced water supply caused by cryospheric change (Barnett et al., 2005). In addition, the loss of cultural values, including spiritual and intrinsic values (Section 2.3.5), can contribute to decisions to migrate (Kaenzig, 2015). Combined with the patterns of permanent emigration, this issue of habitability raises the issue of limits to adaptation in mountain areas (Huggel et al., 2019). Projections of decreased streamflow by 2100 in watersheds with strong glacier meltwater components in Asia, Europe, and North and South America (Section 2.3.1.1) indicate that threats to habitability may continue through this period and affect the endeavours of achieving the sustainable development goals (SDGs) in developing countries (Rasul et al., 2019). 2.4 International Policy Frameworks and Pathways to Sustainable Development The governance of key resources that are affected by climate-related changes in the cryosphere, such as water, is a relevant aspect for climate resilient sustainable development in mountains at the catchment level (Section 2.3.1.4). In this section, we address broader policy frameworks that are expected to shape a solution space through global action. An important development since AR5, at the global level, is the adoption of key frameworks that include the Paris Agreement (UNFCCC, 2015), UN 2030 Agenda and its Sustainable Development Goals (SDGs) (UN, 2015), and the Sendai Framework for Disaster Risk Reduction (UNISDR, 2015), which call for integrated and coordinated climate adaptation action that is also relevant for and applicable in mountain regions. In international climate policy, the importance of averting, minimizing and addressing loss and damage associated with adverse impacts of climate change is articulated in the Paris Agreement under Article 8, more specifically (UNFCCC, 2015). However, despite evident impacts of climate change on the mountain cryosphere (Section 2.3.2), there is limited evidence or reference in the literature to loss and damage for mountains, globally (Huggel et al., 2019). With already committed and unavoidable climate change, its effects on the high-mountain cryosphere (Section 2.2) and related impacts and risks (Section 2.3), substantial adverse effects are expected in the coming decades (Huggel et al., 2019), especially at high emission scenarios, which renders this issue a relevant aspect for planning climate resilient development in mountains. At least in one region, a concrete example for responding to and translating the Paris Agreement in a transboundary mountain setting, is reported. In 2015, through policy measures afforded by the Alpine Convention, the ministers for the environment of the Alpine countries established the Alpine Climate Board, who at the XV Alpine Conference in April 2019, presented a climate target system that includes strategic targets for ‘climate-resilient Alps’ (Hojesky et al., 2019). The implementation and monitoring of these initiatives, however, remains to be assessed on an evidentiary basis. Furthermore, mechanisms afforded through the workplan of the Warsaw International Mechanism, specifically its work area under ‘Noneconomic loss and damage’, are prospects relevant to address impacts to cultural and intrinsic values associated with losses in the high mountain cryosphere (UNFCCC Secretariat, 2014; Serdeczny, 2019). Monitoring and reporting on progress towards sustainable development through the implementation of the SDGs (UN, 2015) is receiving some research attention in the context of mountain regions (Rasul and Tripura, 2016; Gratzer and Keeton, 2017; Bracher et al., 2018; Wymann von Dach et al., 2018 ; Kulonen et al., 2019; Mishra et al., 2019), noting key mountain-specific considerations to improve the conditions under which the SDGs may serve a purpose in the mountain context. For example, previous research has identified a need for disaggregated data for SDG indicators and targets at subnational scales, with relevant area units that are both within country boundaries and/or across borders in transboundary settings (Rasul and Tripura, 2016; Bracher et al., 2018; Wymann von Dach et al., 2018 ). Furthermore, the use of non-standardized proxy data can further limit the potential for comparisons between countries and within regions (Bracher et al., Subject to Copyedit 2-56 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere 2018; Kulonen et al., 2019). On substance, assessments of the economic performance of livelihood options, combined with robust socioeconomic data for mountain systems, are still lacking in many parts of the world, compromising the ability for meaningful comparison and aggregation of data and knowledge for monitoring and reporting on progress of SDGs at regional or global scales (Gratzer and Keeton, 2017). Disasters associated with natural hazards in high mountains are placing many communities and their potential for sustainable development at risk (Wymann von Dach et al., 2017; Keiler and Fuchs, 2018; Vaidya et al., 2019). The Sendai Framework for Disaster Risk Reduction 2015–2030 (UNISDR, 2015) offers a global policy framework under which risks, including climate change, can be accounted for and addressed at national scales. However, there is limited evidence in monitoring and reporting on progress on targets therein (Wymann von Dach et al., 2017), particularly in systematically reporting on root causes of disasters in high mountains and associated compounded risks and cascading impacts, and even more so when accounting for impacts related to climate change. Technical guidelines available for the high-mountain context provide complementary means to monitor and report on the effectiveness of measures to reduce associated risks with changes in the cryosphere (e.g., GAPHAZ, 2017). Other relevant frameworks include the Convention Concerning the Protection of the World Cultural and Natural Heritage, enacted to protect the planet's most significant and irreplaceable places from loss or damage (UNESCO, 1972). In it, conservation strategies are listed that aim at preserving natural and cultural heritage across regions, including sites that contain glaciers (Section 2.3.6), and are suggested as means to further support efforts towards the promotion of knowledge, collective cultural memory, and climate policy (Bosson et al., 2019). Overall, there are promising prospects through international policy frameworks to support governance and adaptation to climate-related changes in the mountain cryosphere whilst addressing sustainable development, with evidence suggesting that treaties and conventions are relevant enablers to support cooperation and implementation at the mountain region scale (Dinar et al., 2016). However, there is limited evidence to systematically assess for effectiveness in addressing specific challenges posed by changes in the mountain cryosphere, globally. 2.5 Key Gaps in Knowledge and Prospects Impacts associated with climate-related changes in the high-mountain cryosphere are evident in the observations reported in this chapter (Section 2.3). However, uncertainties remain with detection and attribution of key atmospheric drivers that influence much of these climate-related changes (Section 2.2.1), due to limited spatial density and/or temporal extent of observation records at high elevations. For example, trends in total or solid precipitation at high elevation remain highly uncertain, due to intrinsic uncertainties with in-situ observation methods, and large natural variability. There are clear knowledge gaps in the distribution and characteristics of cryospheric variables, in particular the extent and ice content of permafrost in mountains but also current glacier ice volumes, trends in lake and river ice, and the spatial and temporal variation of snow cover. These knowledge gaps persist despite a wealth of new data since AR5 especially from Earth observation satellites which overcome much of the remoteness and inaccessibility of high mountains, yet still face challenges for observations in mountains such as dealing with cloud cover and rugged terrain. Along with improved capacities to generate and integrate diverse observation data, initiatives such as citizen science (e.g., Dickerson-Lange et al., 2016; Wikstrom Jones et al., 2018) or Indigenous Knowledge and Local Knowledge (Section 1.8.2, Cross Chapter Box 4 in Chapter 1) can also complement some observations that are based on conventional instruments and models. Radiative forcing effects of light absorbing particles, and understanding their spatiotemporal dynamics, is a key knowledge gap for the attribution of changes in high-mountain snow and glacier and the understanding of regional feedbacks (Section 2.2.2, Box 2.2). These observational knowledge gaps currently impede efforts to quantify trends, and to calibrate and validate models that simulate the past and future evolution of the cryosphere and its impacts. Specific uncertainties are associated with projections of future climate change trends at high elevations due mostly to current limits in regional climate models and downscaling methods to capture the subtle interplays between large-scale climate change and local phenomena influenced by complex topography and high relief (Section 2.2.1). Subject to Copyedit 2-57 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere Coarse-scale simulations of future permafrost conditions in high mountains are fraught with difficulties in capturing fine-scale variation of topography, surface cover and near-surface materials (Section 2.2.4). Improved cross-disciplinary studies bringing together current observation and modelling approaches in each specific field hold potential to contribute to addressing these gaps in the future. Experiences with changes in water availability, and with changes in frequency and/or magnitude of natural hazards, demonstrate the relevance of integrated approaches to understand past impacts and prepare for future risks, where exposure and the underpinning existing vulnerabilities of mountain social-ecological systems influence the extent of these impacts (Section 2.3.2.3). However, there is insufficient understanding of the effects of cryospheric change on some natural hazards such as glacier outburst floods and on infrastructure, for example for transportation. Increased wildfire risk with a shrinking cryosphere is an uncertainty both spatially and temporally and with consequent effects on mountain ecosystems, particularly with respect to soil carbon and potential biome shifts. Overall, few studies have taken a comprehensive risk approach to systematically characterise and compare magnitude and extent of past impacts and future risk across high-mountain regions, including compound risks and cascading impacts where instances of deep uncertainty in responses and outcomes may arise (Cross Chapter Box 5 in Chapter 1). Furthermore, a key knowledge gap is the capacity to economically quantify cryosphere-specific impacts and potential risks. With ecosystems, particularly the terrestrial component, uncertainty exists at which community changes can be directly linked to cryospheric change as distinct from those due to atmospheric warming. In some cases, the changes can be linked, e.g. where a receding glacier creates new habitat, but rising air temperature allow some species to establish that would not otherwise be able to. A major research gap is in our understanding of the fate of legacy pollutants such as mercury downstream of their release from glaciers and permafrost in terms of quantity and regional differences, freshwater sinks, and potential effects to ecosystems and human health. Similarly, the effect of permafrost thaw on water quality and ecosystems due to the increasing release of natural heavy metals and nutrients represents a gap in knowledge. While adaptation measures are reported for high-mountain cryosphere changes (Figure 2.9 a), it stands as a relatively new and developing area of research since AR5 (Figure 2.9 b), with particular gaps in terms of systematically evaluating their cost-benefits and long-term effectiveness as ‘fit-for-purpose’ solutions in the mountain context. Improved inter-comparability of successful adaptation cases, including the transferability of evidence for how adaptation can address both climate change and sustainable development objectives in different mountain regions, are prospects to support an evidentiary basis for future assessments of adaptation to cryosphere changes in the high mountains (Adler et al., 2019; McDowell et al., 2019). Acknowledgements We acknowledge the kind contributions of Matvey Debolskiy (Unversity of Alaska Fairbanks, USA), Florian Hanzer (University of Innsbruck, Austria), Andreas F. Prein (National Center for Atmospheric Research, Boulder, CO, USA), Silvia Terzago (Institute of Atmospheric Sciences and Climate, National Research Council, Torino, Italy) and Natalia Zazulie (CONICET/University of Buenos Aires, Argentina) who contributed to drafting figures. Subject to Copyedit 2-58 Total pages: 94 FINAL DRAFT Chapter 2 IPCC SR Ocean and Cryosphere References Aas, K. S. et al., 2016: The climatic mass balance of Svalbard glaciers: a 10-year simulation with a coupled atmosphere-glacier mass balance model. The Cryosphere, 10 (3), 1089-1104, doi:10.5194/tc-10-1089-2016. Abbott, B. W. et al., 2014: Elevated dissolved organic carbon biodegradability from thawing and collapsing permafrost. Journal of Geophysical Research G: Biogeosciences, 119 (10), 2049-2063, doi:10.1002/2014JG002678. Addor, N. et al., 2014: Robust changes and sources of uncertainty in the projected hydrological regimes of Swiss catchments. 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For some regions, additional estimates are available mostly based on remote sensing data (Table 2.A.1). These estimates were used to derive an average mass change rate for the period 2006-2015 for each glacier region covered in both Chapter 2 and 3. Where several estimates were available for this period or similar periods, these were averaged and uncertainties obtained from standard error propagation assuming the estimates to be independent. The GRACE estimates were only considered in regions with extensive ice cover due to generally large uncertainties in regions with little ice cover (Wouters et al., 2019). The estimates for the polar regions by Box et al. (2018) were not used since they are based on an earlier version of the data by Wouters et al. (2019). Individual regional estimates for overlapping periods between 2000 and 2017 were recalculated to represent the period 2006-2015, prior to averaging with other existing estimates. For Western Canada and USA the mass change rate by Menounos et al. (2019) for 2000-2009 was assumed to hold for 2006-2009, and the rate of -12±5 Gt yr-1 for 2009-2018 was assumed to be valid for 2009-2015. For Iceland the mass change rate by Björnsson et al. (2013) for 2003-2010 was assumed to hold for 2006-2010, and the rate by Foresta et al. (2016) for 2011-2015 was used for the remaining years. The estimate for Iceland by Nilsson et al. (2015) for the period 2003-2009 is similar to the estimate by Björnsson et al. (2013), but was not used since it is based on spatially relatively scarce remote sensing data compared to Björnsson et al. (2013), which is based on detailed glaciological and geodetic balances. The GRACE estimate for Iceland was not used since it deviates strongly from the estimate by Zemp et al. (2019) which is well-constrained by direct observations in this region, while the GRACE estimate may have been affected by the mass change signal from ice masses in southeast Greenland and processes in the Earth mantle cause by isostatic adjustments since the end of the 19th century(Sørensen et al., 2017). For the Low Latitudes (>99% of glacier area in the Andes) available mass loss estimates differ considerably. Zemp et al. (2019)‘s high estimate relies on extrapolation of observations from less than 1% of the glacier area, while the low estimate by Braun et al. (2019) for the Andes may underestimate mass loss due to incomplete coverage and systematic errors in their derived digital elevation models due to radar penetration. In the absence of other estimates for this period the average of both estimates is used. For Arctic Canada and the Southern Andes, the estimates by Zemp et al. (2019) were not considered since they rely on observations from less than 5% of the glacier area. The regional estimates by Gardner et al. (2013) for the period 2003-2009 informed AR5 and are given for comparison but not included in the composite estimate for 2006 - 2015. Table 2A.1. Regional estimates of glacier mass budget in three different units. Only estimates from the studies marked in bold were used to derive the average SROCC estimates. Regional glacier area A and volume V are taken from the Randolph Glacier Inventory (RGI Consortium, 2017) and Farinotti et al. (2019), respectively. Method geod. refers to the geodetic method (using elevation changes) and gl. refers to the glaciological method (based on in-situ mass-balance observations). Results are given for various aggregated areas including among others all regions combined (global), and global excluding the Antarctic (A) and Greenland (G) periphery. All regional estimates (in kg m-2 yr-1) are shown in Figures 2.4 and 3.8). mm SLE yrMass budget kg m-2 yr-1 Gt yr-1 Reference Method 1 Alaska, A=86,725 km2, V=43.3±11.2 mm SLE Subject to Copyedit 2003-2009 -570±200 -50±17 0.14±0.05 Gardner et al. (2013) 1986-2005 -610±280 -53±24 0.15±0.07 Box et al. (2018) 1994-2013 -865±130 -75±11 0.21±0.03 Larsen et al. (2015) 2006-2015 -710±340 -61±30 0.17±0.08 Box et al. (2018) 2006-2015 -570±180 -49±16 0.14±0.04 Wouters et al. (2019) GRACE GRACE, gl. geod. GRACE, gl. GRACE 2006-2015 -830±190 -71±17 0.20±0.05 Zemp et al. (2019) gl., geod. 2-91 Total pages: 94 FINAL DRAFT Western Canada and USA, A=14,524 km2, V=2.6±0.7 mm SLE Iceland, A=11,060 km2, V=9.1±2.4 mm SLE* Scandinavia, A=2949 km2, V=0.7±0.2 mm SLE North Asia, A=2410 km2, V=0.3±0.1 mm SLE Central Europe, A=2092 km2, V=0.3±0.1 mm SLE Caucasus and Middle East, A=1307 km2, V=0.2±0.0 mm SLE High Mountain Asia, A=97,605 km2, V=16.9±2.7 mm SLE Low Latitudes, A=2341 km2, V=0.2±0.1 mm SLE Subject to Copyedit Chapter 2 IPCC SR Ocean and Cryosphere 2006-2015 -700±180 -60±16 0.17±0.04 SROCC 2003-2009 -930±230 -14±3 0.04±0.01 Gardner et al. (2013) gl. 2000-2009 -200±250 -3±3 0.01±0.01 Menounos et al. (2019) geod. 2009-2018 -860±320 -12±5 0.03±0.01 Menounos et al. (2019) geod. 2006-2015 -410±1500 -6±22 0.02±0.06 Wouters et al. (2019) GRACE 2006-2015 -800±400 -11±6 0.03±0.02 Zemp et al. (2019) gl., geod. 2006-2015 -500±910 -8±13 0.02±0.04 SROCC 2003-2009 -910±150 -10±2 0.03±0.01 Gardner et al. (2013) 1986-2005 -360±630 -4±7 0.01±0.02 Box et al. (2018) 1995-2010 -860±140 -10±2 0.03±0.00 Björnsson et al. (2013) GRACE, gl. GRACE, gl. gl. geod. 2003-2010 -995±140 -11±2 0.03±0.00 Björnsson et al. (2013) gl. geod. 2003-2009 -890±250 -10±3 0.03±0.01 Nilsson et al. (2015) geod. 2011-2015 2006-2015 2006-2015 -590±70 -910±190 -620±410 -6±1 -10±2 -7±4 0.02±0.00 0.03±0.01 0.02±0.01 Foresta et al. (2016) Wouters et al. (2019) Zemp et al. (2019) geod. GRACE gl., geod. 2006-2015 -690±260 -7±3 0.02±0.01 SROCC 2003-2009 -610±140 -2±0 0.01±0.00 Gardner et al. (2013) 1986-2005 -120±1170 -0±3 0.00±0.01 Box et al. (2018) 2006-2015 2006-2015 230±3820 -660±270 1±11 -2±1 -0.00±0.03 0.01±0.00 Wouters et al. (2019) Zemp et al. (2019) 2006-2015 -370±1220 -1±4 0.00±0.01 Box et al. (2018) 2006-2015 -660±270 -2±1 0.01±0.00 SROCC 2003-2009 -630±310 -2±0 0.01±0.00 Gardner et al. (2013) gl. 2006-2015 890±1850 2±5 -0.01±0.01 Wouters et al. (2019) GRACE 2006-2015 -400±310 -1±1 0.00±0.00 Zemp et al. (2019) gl., geod. 2006-2015 -400±310 -1±1 0.00±0.00 SROCC 2003-2009 -1060±170 -2±0 0.01±0.00 Gardner et al. (2013) gl. 2006-2015 100±510 0±1 -0.00±0.00 Wouters et al. (2019) GRACE 2006-2015 -910±70 -2±0 0.01±0.00 Zemp et al. (2019) gl., geod. 2006-2015 -910±70 -2±0 0.01±0.00 SROCC 2003-2009 -900±160 -1±0 0.00±0.00 Gardner et al. (2013) gl. 2006-2015 -650±3000 -1±4 0.00±0.01 Wouters et al. (2019) GRACE 2006-2015 -880±570 -1±1 0.00±0.00 Zemp et al. (2019) gl., geod. 2006-2015 -880±570 -1±1 0.00±0.00 SROCC 2003-2009 -220±100 -26±12 -0.07±0.03 Gardner et al. (2013) 2006-2015 -110±140 -11±14 0.03±0.04 Wouters et al. (2019) GRACE, geod. GRACE 2006-2015 -190±70 -18±7 0.05±0.02 Zemp et al. (2019) gl., geod. 2000-2016 -180±40 -16±4 0.04±0.01 Brun et al. (2017) geod. 2006-2015 -150±110 -14±11 0.04±0.03 SROCC 2003-2009 -1080±360 -4±1 0.01±0.00 Gardner et al. (2013) gl. 2000-2013 -230±40 -1±0 0.00±0.00 Braun et al. (2019) geod. 2006-2015 1560±510 4±1 -0.01±0.00 Wouters et al. (2019) GRACE 2-92 gl. GRACE, gl. GRACE gl., geod GRACE, gl. Total pages: 94 FINAL DRAFT Southern Andes, A=29,429 km2, V=12.8±3.3 mm SLE New Zealand, A=1162 km2, V=0.2±0.0 mm SLE Arctic Canada North, A=105,111 km2, V=64.8±16.8 mm SLE Arctic Canada South, A=40,888 km2, V=20.5±5.3 mm SLE Greenland periphery, A=89,717 km2, V=33.6±8.7 mm SLE Svalbard, A=33,959 km2, V=17.3±4.5 mm SLE*** Subject to Copyedit Chapter 2 IPCC SR Ocean and Cryosphere 2006-2015 -940±820 -2±2 0.01±0.00 Zemp et al. (2019) 2006-2015 -590±580 -1±1 0.00±0.00 SROCC 2003-2009 -990±360 -29±10 0.08±0.03 Gardner et al. (2013) GRACE 2006-2015 -1070±240 -31±7 0.09±0.02 Wouters et al. (2019) GRACE 2006-2015 -1300±380 -35±11 0.10±0.03 Zemp et al. (2019) gl., geod 2000-2015 -640±20 -19±1 0.05±0.00 Braun et al. (2019) geod. 2011-2017 -1280±120 -21±2 0.06±0.01 Foresta et al. (2018)** geod. 2006-2015 -860±170 -25±4 0.07±0.01 SROCC 2003-2009 2006-2015 2006-2015 -320±780 110±780 -590±1140 0±1 0±1 -1±1 0.00±0.00 0.00±0.00 0.00±0.00 Gardner et al. (2013) Wouters et al. (2019) Zemp et al. (2019) 2006-2015 -590±1140 -1±1 0.00±0.00 SROCC 2003-2009 -310±40 -33±4 0.09±0.01 Gardner et al. (2013) 1958-1995 -114±110 -12±12 0.03±0.03 Noël et al. (2018) GRACE, geod. Model 1996-2015 -270±110 -28±12 0.08±0.03 Noël et al. (2018) Model 1991-2014 -170±50 -16±2 0.04±0.00 Millan et al. (2017) 1991-2005 -60±20 -6±1 0.02±0.00 Millan et al. (2017) 2005-2014 -340±30 -33±3 0.09±0.01 Millan et al. (2017) 2003-2009 -260±60 -50±9 0.17±0.02 Nilsson et al. (2015) geod. 2006-2015 -400±110 -41±12 0.11±0.03 Noël et al. (2018) Model 2006-2015 -390±30 -41±4 0.12±0.01 Wouters et al. (2019) GRACE 2006-2015 -540±800 -56±84 0.15±0.23 Zemp et al. (2019) gl., geod. 2006-2015 -380±80 -39±8 0.11±0.02 SROCC 2003-2009 -660±110 -27±4 0.07±0.01 Gardner et al. (2013) 1958-1995 -280±100 -12±5 0.03±0.01 Noël et al. (2018) GRACE, geod. Model 1996-2015 -510±100 -22±5 0.06±0.01 Noël et al. (2018) Model 2003-2009 -550±130 -23±5 0.06±0.01 Nilsson et al. (2015) geod. 2006-2015 -650±100 -28±5 0.08±0.01 Noël et al. (2018) Model 2006-2015 -940±210 -39±9 0.11±0.02 Wouters et al. (2019) GRACE 2006-2015 -540±700 -22±28 0.06±0.08 Zemp et al. (2019) gl., geod. 2006-2015 -800±220 -33±9 0.09±0.03 SROCC 2003-2009 -420±70 -38±7 0.10±0.02 Gardner et al. (2013) geod. 1958-1996 1997-2015 -140±190 -400±180 -11±16 -36±16 0.03±0.04 0.10±0.04 Noël et al. (2017) Noël et al. (2017) Model Model 2006-2015 -510±190 -42±16 0.11±0.04 Noël et al. (2017) model 2006-2015 -635±200 -53±17 0.15±0.05 Zemp et al. (2019) gl., geod. 2006-2015 -570±200 -47±16 0.13±0.04 SROCC 2003-2009 -130±60 -5±2 0.01±0.01 Gardner et al. (2013) 1986-2005 -240±120 -8±4 0.02±0.01 Box et al. (2018) 2003-2009 -120±80 -4±3 0.01±0.01 Nilsson et al. (2015) GRACE, geod. GRACE, gl. geod. 2003-2013 -260 -9 0.02 Aas et al. (2016) Model 2004−2013 -210 -7 0.02 Østby et al. (2017) 2006-2015 -250±160 -8±5 0.02±0.02 Box et al. (2018) Model GRACE, gl. 2-93 gl., geod gl. GRACE gl., geod model Total pages: 95 FINAL DRAFT Russian Arctic, A=51,592 km2, V=32.0±8.3 mm SLE Antarctic periphery, A=132,867 km2, V=69.4±18 mm SLE 11 Mountain regions covered in Chapter 2, A=251,604 km2, V=87±15 mm SLE Arctic regions**** A =422,000 km2, V =221±25 mm SLE Global excl. A+G periphery, A=483,155 km2, V=221±23 mm SLE Global, A =705,739 km2, V =324±84 mm SLE Chapter 2 IPCC SR Ocean and Cryosphere 2006-2015 2006-2015 -200±40 -400±230 -7±2 -13±7 0.02±0.00 0.04±0.02 Wouters et al. (2019) Zemp et al. (2019) GRACE gl., geod 2006-2015 -270±170 -9±5 0.02±0.01 SROCC 2003-2009 -210±80 -11±4 0.03±0.01 Gardner et al. (2013) 1986-2005 -210±190 -11±10 0.03±0.03 Box et al. (2018) 2003-2009 -140±50 -7±3 0.02±0.01 Nilsson et al. (2015) GRACE, geod. GRACE, gl. geod. 2006-2015 -200±250 -11±13 0.03±0.04 Box et al. (2018) G., gl. 2006-2015 -220±40 -11±2 0.03±0.01 Wouters et al. (2019) GRACE 2006-2015 -400±370 -20±16 0.06±0.04 Zemp et al. (2019) gl., geod 2006-2015 -300±270 -15±12 0.04±0.03 SROCC 2003-2009 -50±70 -6±10 0.02±0.03 Gardner et al. (2013) geod. 2006-2015 -90±860 -11±108 0.03±0.3 Zemp et al. (2019) gl., geod 2006-2015 -90±860 -11±108 0.03±0.3 SROCC 2006-2015 -490±100 -123±24 0.34±0.07 SROCC 2006-2015 -500±70 -213±29 -0.59±0.08 SROCC 2006-2015 -460±60 -220±30 0.61±0.08 SROCC 2006-2015 -390±160 278±113 0.77±0.31 SROCC Notes: *Björnsson and Pálsson (2008) report a volume of ~9 mm SLE based on radio-echo sounding data. **only Northern and Southern Patagonian Ice Fields (38% of regional area). ***Fürst et al. (2018) report a volume of 15.3±2.6 mm SLE. ****including Alaska, Iceland, and Scandinavia (covered in Chapter 2), and Arctic Canada, Greenland periphery, Russian Arctic and Svalbard (covered in Chapter 3). Subject to Copyedit 2-94 Total pages: 94 FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Chapter 2: High Mountain Areas Supplementary Material Coordinating Lead Authors: Regine Hock (USA), Golam Rasul (Nepal) Lead Authors: Carolina Adler (Switzerland/Australia), Bolívar Cáceres (Ecuador), Stephan Gruber (Canada/Germany), Yukiko Hirabayashi (Japan), Miriam Jackson (Norway), Andreas Kääb (Norway), Shichang Kang (China), Stanislav Kutuzov (Russia), Alexander Milner (UK), Ulf Molau (Sweden), Samuel Morin (France), Ben Orlove (USA), Heidi Steltzer (USA) Contributing Authors: Simon Allen (Switzerland), Lukas Arenson (Canada), Soumyadeep Baneerjee (India), Iestyn Barr (UK), Roxana Bórquez (Chile), Lee Brown (UK), Bin Cao (China), Mark Carey (USA), Graham Cogley (Canada), Andreas Fischlin (Switzerland), Alex de Sherbinin (USA), Nicolas Eckert (France), Marten Geertsema (Canada), Marca Hagenstad (USA), Martin Honsberg (Germany), Eran Hood (USA), Matthias Huss (Switzerland), Elizabeth Jimenez Zamora (Bolivia), Sven Kotlarski (Switzerland), Pierre-Marie Lefeuvre (Norway/France), Juan Ignacio López Moreno (Spain), Jessica Lundquist (USA), Graham McDowell (Canada), Scott Mills (USA), Cuicui Mou (China), Santosh Nepal (Nepal), Jeannette Noetzli (Switzerland), Elisa Palazzi (Italy), Nick Pepin (UK), Christian Rixen (Switzerland), Maria Shahgedanova (UK), S. McKenzie Skiles (USA), Christian Vincent (France), Daniel Viviroli (Switzerland), Gesa Weyhenmeyer (Sweden), Pasang Yangjee Sherpa (Nepal/USA), Nora Weyer (Germany), Bert Wouters (Netherlands), Teppei Yasunari (Japan), Qinglong You (China), Yangjiang Zhang (China) Review Editors: Georg Kaser (Austria), Aditi Mukherji (India/Nepal) Chapter Scientists: Pierre-Marie Lefeuvre (Norway/France), Santosh Nepal (Nepal) Date of Draft: 14 June 2019 Notes: TSU Compiled Version Table of Contents SM2.1 Details of High-Mountain Regional Glacier and Permafrost Areas ........................................... 2 SM2.2 Details of Studies on Temperature Observations and Projections .............................................. 3 SM2.3 Details of Studies on Precipitation Observations and Projections .............................................. 9 SM2.4 Details of Studies on Snow Cover Observations and Projections.............................................. 18 SM2.5 Details on Climate Models used in Figure 2.3 ............................................................................. 23 SM2.6 Synthesis of Recent Studies Reporting on Past and Projected Changes of River Runoff ....... 27 SM2.7 Details of Studies on Peak Water ................................................................................................. 36 SM2.8 Details of Studies on Observed Impacts Attributed to Cryosphere Changes .......................... 39 SM2.9 Details of Studies on Adaptations in Response to Cryosphere Changes................................... 50 References ....................................................................................................................................................... 70 Do Not Cite, Quote or Distribute SM2-1 Total pages: 87 FINAL DRAFT SM2.1 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Details of High-Mountain Regional Glacier and Permafrost Areas The regional glacier and permafrost areas shown in Figure 2.1 are listed in Table SM2.1. Glacier area is taken from the Randolph Glacier Inventory (RGI6.0, RGI Consortium (2017)) and includes all glaciers within the depicted region boundaries, whereas permafrost area includes only the permafrost in mountains. Regional permafrost area is calculated on a grid with 30 arc-second resolution (~1km), as the sum of fractional permafrost area multiplied by the area of each grid cell; permanent snow and ice are masked based on landcover data from the European Space Agency Climate Change Initiative (ESA CCI Land Cover). The areas are then masked by the regions outlined in Figure 2.1 and by a ruggedness index larger than 3.5 (Gruber, 2012) which, in this chapter, defines mountains. Two global-scale permafrost modeling studies (Gruber, 2012; Obu et al., 2019) provide suitable data with models differing in input, model structure, and assumptions. The data by Obu et al. (2019), extended to the southern hemisphere, are used since they provide permafrost fractional area (permafrost probability) directly. Their model was forced by remotely-sensed land-surface temperature, land cover and ERA-Interim climate reanalysis data, and statistically accounted for subgrid variability of ground temperature due to snow and landcover. By contrast, (Gruber, 2012)used heuristics and mean annual air temperature to derive an approximate index of fractional permafrost area. Bounds of uncertainty were estimated by using two forcing climate data sets (reanalysis data from National Centers for Environmental Prediction (NCEP) and data from the Climatic Research Unit, CRU TS 2.0), and several sets of model parameters, resulting in five maps in total. Assuming the index to represent the fractional permafrost area, aggregated results for high-mountain permafrost areas are similar to the estimate based on Obu et al. (2019). For high-mountain areas, the five models by Gruber (2012) yield areas varying from 3.6 to 5.2 million km2 and the model of Obu et al. (2019) results in 3.7 million km2. The percentage of permafrost in high-mountain areas relative to the global permafrost area, computed separately for each model, is 27–29% for Gruber (2012) and 27% for Obu et al. (2019). Table SM2.1: Glacier and permafrost area in high-mountain regions shown in Figure 2.1. Glacier area is from the Randolph Glacier Inventory (RGI6.0, RGI Consortium (2017)). Permafrost areas are based on Obu et al. (2019). High Mountain Region Glacier Area Permafrost Area (km2) (km2) Alaska 86,725 307,767 Western Canada and USA 14,524 256,254 Iceland 11,060 4,023 Scandinavia 2,949 8,306 Central Europe 2,092 7,124 Caucasus and Middle East 1,307 10,181 North Asia 2,410 2,234,058 High Mountain Asia 97,605 866,667 Low Latitudes 2,341 673 Southern Andes 29,429 27,172 New Zealand 1,162 180 All high-mountain regions 251,614 3,722,405 Do Not Cite, Quote or Distribute SM2-2 Total pages: 87 FINAL DRAFT SM2.2 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Details of Studies on Temperature Observations and Projections Table SM2.2: Overview of studies reporting trends in past surface air temperature including mean annual, seasonal and monthly mean values of daily mean, minimum and maximum temperature, per high mountain region (as defined in Figure 2.1) with published observations. Global syntheses are listed at the top of the table. Obs. stations refers to observation stations. Elevations are in meters (m) above sea level. Location Temperature (temp.) indicator Trend Time Dataset Reference (°C per period decade) Global syntheses >500 m, 30–70˚N Annual mean value of minimum daily temp. +0.21 1951–1989 250 obs. stations Diaz and Bradley (1997) <500 m, 30–70˚N Annual mean value of minimum daily temp. +0.04 “ 993 obs. stations “ >500 m with mean annual temp. Mean annual temp. +0.23 1948–2002 269 obs. stations Pepin and Lundquist (2008) from -5 to +5˚C >500 m with mean annual temp. Mean annual temp. +0.12 “ 1084 obs. stations “ <-5 or >+5°C > 500 m Mean annual temp. +0.40 1982–2010 640 obs. stations Zeng et al. (2015) < 500 m Mean annual temp. +0.32 “ 2020 obs. stations “ > 500 m Mean annual temp. +0.30 1961–2010 910 obs. stations Wang et al. (2016) < 500 m Mean annual temp. +0.24 “ 1742 obs. stations “ > 500 m Winter mean temp. +0.4 1961–2010 739 obs. stations Qixiang et al. (2018) < 500 m Winter mean temp. +0.35 “ 1262 obs. station “ Western Canada and USA Colorado and Pacific Northwest, Annual mean value of minimum daily temp. +0.37 1979–2006 Gridded dataset (based on Diaz and Eischeid (2007) < 4000 m obs. stations without homogenization) > 4000 m Annual mean value of minimum daily temp. +0.75 “ “ “ Mt. Washington, NE USA, 1905 m Mean annual temp. +0.35 1970–2005 1 obs. station Ohmura (2012) Pinkham Notch, NE USA, 613 m Mean annual temp. +0.31 “ 1 obs. station “ NW USA Annual mean value of minimum daily temp. +0.17 1981–2012 Gridded dataset (based on Oyler et al. (2015) homogenized obs. station) Whole N America, > 500 m Mean annual temp. +0.14 1948–1998 552 obs. stations Pepin and Seidel (2005) Central Europe Switzerland Mean annual temp. +0.35 1959–2008 Gridded dataset (based on 91 Ceppi et al. (2012) homogenized obs. stations) “ Autumn mean temp. +0.17 “ “ “ “ Winter mean temp. +0.40 “ “ “ “ Spring mean temp. +0.39 “ “ “ “ Summer mean temp. +0.46 “ “ “ Do Not Cite, Quote or Distribute SM2-3 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Switzerland Mean annual temp. +0.13 1864–2016 Switzerland, 203–815 m Switzerland, 910–1878 m Switzerland, 1968–3850 m Swiss Alps Jungfraujoch, 3580 m Sonnblick, 3109 m Col de Porte, 1325 m Mont-Blanc, 4300 m Trentino, 203–875 m Trentino, 925–2125 m Abruzzo Region Central Pyrenees “ “ “ Caucasus and Middle East Whole area “ Central Palestinian Mountains Southern Andes 18°S to 42°S Central Andes, 10°S–25°S, free atmosphere (500 hPa) Subtropical Andes, 30°S–37°S “ “ “ Low latitudes (Andes and Africa) Tropical Andes, 2°N–18°S La Paz, Bolivia East Africa “ South and East Africa, > 500 m High Mountain Asia Hindu Kush-Himalaya “ Mukteshwar, India, 2311 m Toutouhe, China, 4535 m Mean annual temp. “ “ Mean April temp. Mean annual temp. Mean annual temp. Winter mean temp. (December–April) Mean temp. (from englacial obs.) Mean annual temp. “ Mean annual temp. Annual mean value of maximum daily temp. “ Annual mean value of minimum daily temp. “ +0.35 +0.31 +0.25 +0.51 +0.43 +0.30 +0.3 +0.14 +0.49 +0.27 +0.15 +0.11 +0.57 +0.06 +0.23 Mean annual temp. “ Mean annual temp. Mean annual temp. Mean annual temp. Do Not Cite, Quote or Distribute Begert and Frei (2018) 1981–2017 “ “ 1961–2011 1970–2011 1980–2011 1960–2017 1900–2004 1976–2010 “ 1951–2012 1910–2013 1970–2013 1910–2013 1970–2013 Gridded dataset (based on 19 homogenized obs. stations) 47 obs. stations 34 obs. stations 12 obs. stations 6 obs. stations 1 obs. station 1 obs. station 1 obs. station 1 obs. site 12 obs. stations 12 obs. stations 24 obs. stations 155 obs. stations “ “ “ +0.14 +0.26 +0.33 1958–2000 1974–1998 1970–2011 Reanalysis data “ 6 obs. stations Diaz et al. (2003) “ Hammad and Salameh (2019) 1950–2010 1979–2008 75 obs. stations Reanalyses Vuille et al. (2015) Russell et al. (2017) Winter mean temp. “ Summer mean temp. “ -0.05 +0.16 to +0.41 +0.4 +0.2 +0.3 No trend 1980–2005 “ “ “ Reanalysis Gridded observation dataset Reanalysis Gridded observation dataset Zazulie et al. (2017) “ “ “ Mean annual temp. Mean annual temp. Mean annual temp. “ Mean annual temp. +0.13 -0.70 +0.18 +0.18 +0.14 1950–2010 1985–2010 1958–2000 1974–1998 1948–1998 546 obs. stations 1 obs. station Reanalysis “ 41 obs. stations Vuille et al. (2015) Ohmura (2012) Diaz et al. (2003) Mean annual temp. “ Mean annual temp. Mean annual temp. +0.1 +0.2 +0.48 +0.02 1901–2014 1951–2014 1980–2010 1970–2005 122 obs. stations “ 1 obs. station 1 obs. station Krishnan et al. (2019) “ Ohmura (2012) “ SM2-4 Total pages: 87 Rottler et al. (2019) “ “ Scherrer et al. (2012) Ohmura (2012) “ Lejeune et al. (2019) Gilbert and Vincent (2013) Tudoroiu et al. (2016) “ Scorzini and Leopardi (2019) Pérez-Zanón et al. (2017) “ “ “ Pepin and Seidel (2005) FINAL DRAFT Himalaya “ Tibetan Plateau “ Tibetan Plateau, > 3000 m Tibetan Plateau, 1000–3000 m Tibetan Plateau, 4500–5000 m “ Tibetan Plateau, > 2000 m “ Tibetan Plateau, > 2000 m “ China 600–800m Tibetan Plateau, 2400–2600 m Tibetan Plateau, 4200–4400 m Tibetan Plateau, > 2000 m Tibetan Plateau, > 2000 m “ “ Tibetan Plateau “ Indian Himalaya Himalaya (Nepal), 1200–2000 m Himachal Pradesh Kashmir Australia Australia, > 500 m Japan Fuji San, 3775 m Do Not Cite, Quote or Distribute Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Mean annual temp. “ Mean temp., wet season (May–Sep) Mean temp., dry season (Oct–Apr) Mean annual temp. “ Mean value of winter minimum daily temp. Annual mean value of minimum daily temp. Mean value of winter minimum daily temp. Annual mean value of minimum daily temp. Mean annual temp. Winter mean temp. Mean annual temp. Mean annual temp. Mean annual temp. Mean annual temp. Winter mean temp. Summer mean temp. Mean annual temp. Winter mean temp. Summer mean temp. Mean annual temp. Mean annual temp. Annual mean value of maximum daily temp. Winter mean temp. Winter mean temp. +0.06 +0.23 +0.40 +0.54 +0.69 +0.55 +0.85 +0.53 +0.61 +0.42 +0.16 +0.32 +0.05 +0.15 +0.25 +0.28 +0.40 +0.20 +0.25 +0.37 +0.17 +0.23 +0.16 +0.57 +0.23 +0.2 1958–2000 1974–1998 1979–2011 “ 1981–2006 “ 1961–2006 “ “ “ 1955–1996 “ 1961–1990 “ “ 1961–2007 1961–2004 “ “ 1961–2001 “ “ 1901–2002 1963–2009 1975–2006 1975–2006 Reanalysis “ 83 obs. stations “ 47 obs. stations 24 obs. stations Obs. stations. Obs. stations. 116 obs. stations. “ 97 obs. stations 97 obs. stations 12 obs. stations 4 obs. stations 6obs. stations 72 obs. stations 71 obs. stations “ “ ERA40 Reanalysis “ “ 3 obs. stations 3 obs. station 4 obs. stations 12 obs. stations Diaz et al. (2003) “ Gao et al. (2015) “ Qin et al. (2009) “ Liu et al. (2009) “ “ “ Liu and Chen (2000) “ “ “ “ Guo et al. (2012) You et al. (2010a) “ “ You et al. (2010b) “ “ Bhutiyani et al. (2007) Nepal (2016) Dimri and Dash (2012) “ Mean annual temp. +0.16 1948–1998 14 obs. stations Pepin and Seidel (2005) Mean annual temp. +0.35 1985–2005 1 obs. station Ohmura (2012) SM2-5 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Table SM2.3: Overview of studies reporting future trends in surface air temperature including mean annual, seasonal and monthly mean values of daily mean, minimum and maximum temperature, per high mountain region (as defined in Figure 2.1). Global syntheses are listed at the top of the table. Obs. stations refer to observation stations. Elevations are in meters (m) above sea level. Location Temperature (temp.) Change Time period Scenario Method Reference indicator (˚C per decade) Global scale 13 mountain ranges Mean annual temp. +0.48 1961–1990 vs 2070– SRES-A1F1 Downscaled GCMs Nogués-Bravo et al. (2007) 2099 13 mountain ranges Mean annual temp. +0.25 1961–1990 vs 2070– SRES B1 “ “ 2099 Alaska N America, >55°N Mean annual temp. +0.61 1961–1990 to 2070– SRES A1F1 Downscaled GCMs Nogués-Bravo et al. (2007) 2099 “ “ +0.35 “ SRES B1 “ “ Western Canada and USA Colorado Rockies Spring temp. (April) up to +1 1995–2005 to 2045– SRES A2 Pseudo-GW runs: Letcher and Minder (2015) 2055 RCMs N America, <55°N Mean annual temp. +0.49 1961–1990 to 2070– SRES A1F1 Downscaled GCMs Nogués-Bravo et al. (2007) 2099 N America, <55°N Mean annual temp. +0.27 “ SRES B1 “ “ Iceland Full domain Mean annual temp. +0.21 to +0.40 2000–2100 RCP8.5 Downscaled GCMs Gosseling (2017) using RCMs Central Europe European Alps Mean annual temp. +0.25 1961–1990 to 2021– SRES A1B Downscaled GCMs Gobiet et al. (2014) 2050 using RCMs “ “ +0.36 1961–1990 to 2069– “ “ “ 2098 Switzerland Mean annual temp. +0.14 1981–2010 to 2070– RCP2.6 Downscaled GCMs CH2018 (2018) 2099 using RCMs (EURO-CORDEX) “ “ +0.26 “ RCP4.5 “ “ “ “ +0.49 “ RCP8.5 “ “ Austria Mean annual temp. +0.23 1971–2000 to 2071– RCP4.5 Downscaled GCMs Chimani et al. (2016) 2100 using RCMs (EURO-CORDEX) “ “ +0.4 “ RCP8.5 “ “ Scandinavia Whole area, < 500 m Winter mean temp. +0.45 1961–1990 to 2070– SRES A1B Downscaled GCMs Kotlarski et al. (2015) 2099 using RCMs Do Not Cite, Quote or Distribute SM2-6 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material Whole area, ~1500 m Whole area Summer mean temp. Mean annual temp. +0.27 +0.54 “ “ +0.31 Caucasus and Middle East Iran mountain areas Mean annual temp. +0.45 “ North Asia Whole area “ +0.30 Mean annual temp. +0.76 “ Southern Andes Whole area “ +0.43 Mean annual temp. +0.34 “ “ “ Low Latitudes (Andes) Tropical Andes “ Winter and summer temp. “ +0.18 +0.2 ~+0.5 Mean annual temp. +0.3 Bolivian Andes Mean annual temp. +0.34 to +0.4 “ “ +0.38 to +0.44 Quelccaya ice cap, Peru, 5680 m “ High-Mountain Asia Himalaya/ Tibetan Plateau, ~1600 m Himalaya/ Tibetan Plateau, ~4100 m Hindu-Kush Himalaya Mean annual temp. Himalaya Do Not Cite, Quote or Distribute IPCC SR Ocean and Cryosphere “ 1961–1990 to 2070– 2099 1961–1990 to 2070– 2099 “ SRES A1F1 “ Downscaled GCMs “ Nogués-Bravo et al. (2007) SRES B1 Downscaled GCMs “ 1961–1990 to 2071– 2000 “ SRES A2 Downscaled GCM Babaeian et al. (2015) SRES B2 “ 1961–1990 to 2070– 2099 “ SRES A1F1 Downscaled GCMs Nogués-Bravo et al. (2007) SRES B1 “ “ 1961–1990 to 2070– 2099 “ 2006–2100 “ SRES A1F1 Downscaled GCMs Nogués-Bravo et al. (2007) SRES B1 RCP4.5 RCP8.5 “ CMIP5 GCMs “ “ Zazulie et al. (2018) “ RCP8.5 Downscaled GCMs Vuille et al. (2018) SRES A1B Downscaled GCMs Rangecroft et al. (2016) “ “ “ +0.25 1961–2000 to 2080– 2100 1950–2000 to 2040– 2069 1950–2000 to 2070– 2099 2006–2100 RCP4.5 Yarleque et al. (2018) “ +0.57 “ RCP8.5 Bias corrected CMIP5 GCMs “ Mean value of winter minimum daily temp. “ +0.32 1971–2000 to 2071– 2100 “ RCP8.5 CMIP5 GCMs Palazzi et al. (2017) “ “ “ Winter mean temp. +0.6 RCP8.5 RCMs Sanjay et al. (2017) Summer mean temp. Winter mean temp. +0.54 +0.57 “ RCP8.5 “ RCMs “ Dimri et al. (2018) Summer mean temp. +0.45 1976–2005 to 2066– 2095 “ 1970–2005 to 2070– 2099 “ “ “ “ SM2-7 +0.75 Total pages: 87 FINAL DRAFT Tibetan Plateau, ~4500 m Tibetan Plateau, 2000–2200 m Kashmir Himalaya Chapter 2 Supplementary Material Mean annual temp. “ Annual mean value of minimum daily temp. “ “ +0.65 +0.51 +0.07 “ Annual mean value of maximum daily temp. “ “ +0.15 +0.11 “ New Zealand New Zealand “ +0.22 Mean annual temp. +0.33 “ “ +0.17 “ “ “ “ “ “ Do Not Cite, Quote or Distribute SM2-8 +0.13 +0.04 +0.19 +0.08 IPCC SR Ocean and Cryosphere 2006–2050 “ 1980–2010 to 2041– 2070 “ 1980–2010 to 2071– 2100 “ 1980–2010 to 2041– 2070 “ 1980–2010 to 2071– 2100 “ RCP8.5 “ RCP2.6 Downscaled GCMs “ Downscaled GCM Guo et al. (2016) “ Shafiq et al. (2019) RCP8.5 RCP2.6 “ “ “ “ RCP8.5 RCP2.6 “ “ “ “ RCP8.5 RCP2.6 “ “ “ “ RCP8.5 “ “ 1961–1990 to 2070– 2099 1961–1990 to 2070– 2099 SRES A1F1 Downscaled GCMs Nogués-Bravo et al. (2007) SRES B1 Downscaled GCMs “ Total pages: 87 FINAL DRAFT SM2.3 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Details of Studies on Precipitation Observations and Projections Table SM2.4: Overview of recent studies providing evidence for past changes in precipitation, per high mountain region (as defined in Figure 2.1). Obs. stations refer to observation stations. Elevations are in meters (m) above sea level. Location Precipitation (precip.) indicator Change Time Dataset Reference period Alaska Alaska Annual precip. Increase +8% to +40%, depending on 1949–2016 18 obs. stations Wendler et al. (2017) the region Western Canada and USA California Winter precip. Insignificant 1920–2014 Gridded dataset based on Mao et al. (2015) 102 obs. stations Canada Ratio of snowfall to total precip. Decrease, more pronounced in 1948–2012 Gridded dataset based on Vincent et al. (2015) Western Canada obs. stations Iceland Whole area Winter precip. Insignificant 1961–2000 Reanalysis and 40 obs. Crochet (2007) stations Central Europe European Alps Total precip. Insignificant, dominated by internal 1901–2008 Gridded dataset based on Masson and Frei variability obs. stations (2016) European Alps Daily precip. Insignificant change due to high 1980–2010 43 obs. stations Kormann et al. variability (2015a) Swiss Alps Fraction of days with snowfall -20 % 1961–2008 Subset within 52 obs. Serquet et al. (2011) over days with precip. (annual), stations <1000 m “ “, 1000–2000 m -10% to -20% “ “ “ “ “, >2000 m -5% “ “ “ “ Fraction of days with snowfall -30 to -50 % “ Subset within 28 obs. “ over days with precip. (spring), stations <1000 m “ “, 1000–2000 m -10% to -30% “ “ “ “ “, >2000 m -5% to -10% “ “ “ Abruzzo Region Total precip. -1.8%/dec. (not significant) 1951–2012 46 obs. stations Scorzini and Leopardi (2019) Pyrenees Total precip. Insignificant decrease (-0.6%/decade) 1950–1999 24 obs. stations López-Moreno (2005) Carpathian mountain regions Total precip. No significant trend 1961–2010 Gridded data based on obs. Spinoni et al. (2015) stations. Scandinavia Do Not Cite, Quote or Distribute SM2-9 Total pages: 87 FINAL DRAFT Finland Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Annual snowfall over total precip. ratio Decrease (-1.9% per decade) 1909–2008 3 obs. stations Irannezhad et al. (2017) Total precip. -9 mm yr-1 1936–2012 90 obs. stations Adjara mountains Southern Andes Chile and Argentina “ +6 mm yr-1 “ Subset of 90 obs. stations Elizbarashvili et al. (2017) “ Annual precip. 1979–2010 Gridded dataset from obs. stations, and reanalyses Rusticucci et al. (2014) Subtropical Andes, 30°S–37°S Winter precip. General decrease (up to ~ -6 mm yr-1) with positive values in the southwest corner of the region < -0.1 mm d-1 per dec, insignificant 1980–2005 Zazulie et al. (2017) -0.1 mm d-1 per dec -0.3 mm d-1 per dec, insignificant -0.2 mm d-1 per dec, insignificant 1980–2005 1980–2005 1980–2005 Gridded dataset from obs. stations, and reanalyses “ “ “ Insignificant 1981–2003 7 obs. stations Ruiz et al. (2008) Insignificant, except decrease in Africa 1982–2006 Gridded dataset from obs. stations, and reanalyses Krishnaswamy et al. (2014) Decrease (March to May, long rains) and increase (October to December, short rains). 1979–2011 50 obs. stations Schmocker et al. (2016) Annual precip. “ -0.14 mm yr-1 +0.89 mm yr-1 1966–2015 “ 9 obs. stations 8 obs. stations Zhang et al. (2018) “ Precip. (December to April) Insignificant 1950–2010 Palazzi et al. (2013) -0.021 mm d-1 yr-1 to -0.01 mm d-1 yr- 1950–2009 Gridded dataset from obs. station, and reanalyses “ Archer and Fowler (2004) Chen et al. (2016) Caucasus and Middle East Greater Caucasus “ “ “ Summer precip. “ “ Low Latitudes (Andes and Africa) Claro River (Colombian Annual precip. Andean Central mountain range) 47 mountain protected areas in Annual precip. five National Parks in the tropical belt (30°S–30°N, including Central America, South America, Africa, South Asia, Southeast Asia) Kenya Mean precip. North Asia Northern Altai Southern Altai High Mountain Asia Hindu-Kush Karakoram Himalaya Precip. (June to September) Karakoram Winter precip. Significant increasing trend 1961–1999 17 obs. stations Middle and East Tian Shan Snowfall fraction Decrease, from 27% to 25% 1960–2014 Gridded dataset based on obs. stations Do Not Cite, Quote or Distribute SM2-10 1 Total pages: 87 “ “ “ “ FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere West Tian Shan Monsoon-dominated regions, easternmost Himalaya “ Northwestern Indian Himalaya Winter total precip. Annual precip. trend +23% -13.7 ± 2.4 mm yr-1 1960–2014 1994–2012 In-situ 7 obs. stations “ Salerno et al. (2015) Precip. during monsoon months Snowfall fraction “ 1991–2005 “ 10 obs. stations “ Winter precip. trend 1866–2006 Subset of 10 obs. stations “ Bhutiyani et al. (2010) “ “ Tibetan Plateau Monsoon and annual precip. trend Annual precip. “ 1960–2014 “ 71 obs. stations “ Deng et al. (2017) Hengduan Mountain region Hindu Kush-Himalaya Annual precip. Springtime precip. Precip. >95th, precip. intensity -9.3 mm yr-1 Significant decreasing trend (3 out of 7 stations) Increasing but statistically insignificant Significant decreasing +1.43 mm yr-1, large spatial variations Insignificant decrease Insignificant increase Insignificant changes 1961–2011 “ 1960–2000 90 obs. stations “ Gridded datasets using obs. stations, 5 specific obs. stations Xu et al. (2018) “ Panday et al. (2015) New Zealand and Australia New Zealand Total precip. amount 1900–2010 294 obs. stations 1901–2012 Obs. stations Caloiero (2014); Caloiero (2015) Grose et al. (2015) Obs. stations (61 at daily time resolution) “ SE Australia Japan Whole region Total annual precip. Absence of marked trends, seasonally and geographically variable Reduction since 1970s Intense precip. +30 % per century 1898–2003 “ Weak precip. -20% per century “ Do Not Cite, Quote or Distribute SM2-11 Total pages: 87 Fujibe et al. (2005) “ FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Table SM2.5: Overview of recent studies providing evidence for future changes in precipitation, per high mountain region (as defined in Figure 2.1). Obs. stations refer to observation stations. Elevations are in meters (m) above sea level. Location Precipitation (precip.) Change Time period Scenario Method Reference indicator Alaska South and Snow day fraction -15% to +7% 1970–1999 to 2040– RCP4.5 Statistically Littell et al. (2018) Southeast Alaska 2069 downscaled GCMs “ “ -25% to +4% “ RCP8.5 “ “ “ “ -22% to 4 % 1970–1999 to 2070– RCP4.5 “ “ 2099 “ “ -41% to -6 % “ RCP8.5 “ “ Western Canada and USA Western US, Snowfall amount -70% to -35% 1950-2005 to 2040-2069 RCP8.5 Statistically Lute et al. (2015) “Warm mountain downscaled GCMs sites” Western US, “Cold “ -20 % to -5 % “ “ “ “ mountain sites” Western US, 90% percentile of -30 % “ “ “ “ “Warm mountain snowfall events sites” Western US, “Cold 90% percentile of +5 % “ “ “ “ mountain sites” snowfall events Southern California Total winter snowfall; -40% 1981–2000 to 2041– RCP2.6 Downscaled GCMs Sun et al. (2016) 1500–2000 m 2060 “ “ ; 2000–2500 m -22% “ “ “ “ “ “ ; >2500 m -8% “ “ “ “ “ Total winter snowfall; -52% “ RCP8.5 “ “ 1500–2000 m “ “ ; 2000–2500 m -28% “ “ “ “ “ “ ; >2500 m -11% “ “ “ “ “ Total winter snowfall; -43% 1981–2000 to 2081– RCP2.6 “ “ 1500-2000 m 2100 “ “ ; 2000–2500 m -26% “ “ “ “ “ “ ; >2500 m -13% “ “ “ “ “ Total winter snowfall; -78 % “ RCP8.5 “ “ 1500-2000 m “ “ ; 2000–2500 m -48% “ “ “ “ “ “ ; >2500 m -18% “ “ “ “ Western Canada Winter precip. +11% 1979–1994 to 2045– RCP8.5 Downscaled GCMs Erler et al. (2017) 2060 Do Not Cite, Quote or Distribute SM2-12 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere “ “ +17% 1979–1994 to 2085– 2100 “ “ “ Iceland Whole area Total precip. Insignificant 1981–2000 to 2081– 2100 RCP4.5, RCP8.5 Downscaled GCMs using RCMs Gosseling (2017) Winter precip. +12.3% RCP4.5 Spring precip. Summer precip. Fall precip. Number of days with precip. > 15 mm Mean winter (December to February) precip. +5.7% -1.7% +2.3% +10.9% 1971–2000 to 2071– 2100 “ “ “ “ 5 EUROCORDEX GCM/RCM pairs “ “ “ “ Smiatek et al. (2016) “ “ “ “ +8 % 1981–2010 to 2020– 2049 RCP4.5 Rajczak and Schär (2017) “ “ “ “ +6 % +12 % RCP8.5 RCP4.5 “ Switzerland “ Annual mean precip. +17% +0.6 % Winter (December to February) mean precip. Annual mean precip. Winter (December to February) mean precip. Annual mean precip. Winter (December to February) mean precip. Annual mean precip. +8.8% “ “ EUROCORDEX GCM/RCM pairs “ “ CH2018 (2018) “ “ 1981–2010 to 2070– 2100 “ 1981–2010 to 2070– 2099 “ EUROCORDEX GCM/RCM pairs (0.11°) “ “ +3% +12.9% “ “ RCP4.5 “ “ “ “ “ +3.3% +23.7% “ “ RCP8.5 “ “ “ “ “ +7.1% RCP4.5 Winter (December to February) mean precip. Annual mean precip. Winter (December to February) mean precip. Annual solid precip. Amount +10.6% 1971–2000 to 2071– 2100 “ “ EUROCORDEX GCM/RCM pairs “ Chimani et al. (2016) “ +8.7% +22.7% “ “ RCP8.5 “ “ “ “ “ -25 % 1981–2010 to 2070– 2099 RCP4.5 EUROCORDEX GCM/RCM pairs (0.11°) Frei et al. (2018) Central Europe Greater Alpine Region “ “ “ “ Alpine Region “ “ “ “ Austria “ “ “ Alps Do Not Cite, Quote or Distribute SM2-13 “ “ “ “ RCP8.5 RCP2.6 Total pages: 87 “ “ “ FINAL DRAFT “ Pyrenees, <1500 m Chapter 2 Supplementary Material “ Dynamically downscaled GCM “ “ López-Moreno et al. (2011) “ SRES B2 RCP8.5 “ Multiple GCM/RCM pairs “ Alberton et al. (2017) 1961–1990 to 2071– 2100 SRES A1B Multiple GCM/RCM pairs Räisänen and Eklund (2012) 1961–1990 to 2071– 2000 “ 1981–2000 to 2081– 2100 SRES A2 Downscaled GCM Babaeian et al. (2015) SRES B2 RCP4.5, RCP8.5 “ 3 CMIP5 GCMs No clear trend 2006–2100 GCMs Geographically variable. Precip. increase up to ~2000 m. No significant changes on eastern slope >2000 m, decrease in the western slope >4000 m -19% to -33% 1961–1990 to 2071– 2100 RCP4.5, RCP8.5 SRES A2, B2 1961-2010 to 2071-2100 RCP8.5 Multiple GCMs Neukom et al. (2015) High-Mountain Asia Himalaya Summer precip. +0.008 to +0.014 mm d-1 yr-1 2006–2100 RCP8.5 Eastern Himalaya Annual precip. +15 to +27% (most in summer) Western HimalayaKarakoram Hindu Kush Himalaya Northwest Himalaya and Karakoram Annual precip. +1 to +5% (due to increase in winter precip.) +50% on average 1970–1999 to 2070– 2099 “ SRES B1, A1B, A2 and RCP8.5 “ GCM multimember ensemble CMIP3 and CMIP5 GCMs “ Palazzi et al. (2013) Panday et al. (2015) “ 1981–2010 to 2071– 2100 1976–2005 to 2036– 2065 RCP8.5 Downscaled GCMs RCP4.5 CORDEX GCM/RCM pairs Wijngaard et al. (2017) Sanjay et al. (2017) Pyrenees, >2000 m “ Frequency and intensity of heavy snowfall events “ Pyrenees, > 2000 m “ Carpathian Summer mean precip. mountains Scandinavia Scandinavian Annual snowfall mountains (high elevation) Caucasus and Middle East Iran mountain areas Mean precip. “ Alborz mountains “ Annual precip., winter precip. Low Latitudes (Andes) Subtropical Andes, Winter and summer 30°S-37°S precip. Tropical Andes Annual precip. Central Andes Annual precip. Daily 99% precip. quantile Precip., June to September Do Not Cite, Quote or Distribute -45% Decrease IPCC SR Ocean and Cryosphere “ 1960–1990 to 2070– 2100 “ RCP8.5 SRES A2 “ 1971–2000 to 2071– 2100 +20% Precip. increase Insignificant except at high altitude (+30% increase) +20-30% Decrease by up to -20 mm per month “ No significant change detected -0.1% SM2-14 “ Total pages: 87 Downscaled GCM Zarenistanak (2018) Zazulie et al. (2018) Urrutia and Vuille (2009) FINAL DRAFT “ “ “ “ “ “ “ Central Himalaya “ “ “ “ “ “ “ Southeast Himalaya and Tibetan Plateau “ “ “ “ Chapter 2 Supplementary Material Precip., December to April Precip., June to September Precip., December to April Precip., June to September Precip., December to April Precip., June to September Precip., December to April Precip., June to September Precip., December to April Precip., June to September Precip., December to April Precip., June to September Precip., December to April Precip., June to September Precip., December to April Precip., June to September Precip., December to April Precip., June to September Precip., December to April Precip., June to September Do Not Cite, Quote or Distribute IPCC SR Ocean and Cryosphere +7% “ “ “ “ +3.5% 1976–2005 to 2066– 2095 “ “ “ “ “ “ “ 1976–2005 to 2036– 2065 “ RCP8.5 “ “ “ “ “ 1976–2005 to 2066– 2095 “ “ “ “ “ “ “ 1976–2005 to 2036– 2065 “ RCP4.5 “ “ “ “ “ 1976–2005 to 2066– 2095 “ “ “ “ “ “ “ 1976–2005 to 2036– 2065 “ RCP8.5 “ “ “ “ “ 1976–2005 to 2066– 2095 “ “ “ “ “ “ “ 1976–2005 to 2036– 2065 “ RCP4.5 “ “ “ “ “ 1976–2005 to 2066– 2095 “ “ “ “ “ “ “ 1976–2005 to 2036– 2065 RCP8.5 “ “ +14.1% +3.7% +12.8% +3.9% 12.9% 4.4% -0.7% +10.5% +1.5% +9.1% -1.3% +19.1% -8.8% +6.8% +3.1% +10.4% +3.7% 10.2% SM2-15 Total pages: 87 FINAL DRAFT “ Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere +0.9% “ “ “ “ 22.6% 1976–2005 to 2066– 2095 “ “ “ “ “ “ “ Tibetan Plateau Precip., December to April Precip., June to September Precip., December to April Total precip. Su et al. (2013) “ +6% RCP2.6, RCP8.5 RCP2.6 CMIP5 GCMs “ “ “ “ Eastern Tibetan Plateau Kashmir Himalaya “ Annual snowfall +12% -15% RCP8.5 RCP4.5 +9% RCP2.6 “ RCM driven by several GCMs Downscaled GCM “ Zhou et al. (2018) Annual precip. “ “ “ “ +12% +11% RCP8.5 RCP2.6 “ “ “ “ “ Northern Tian Shan “ Total precip. +14% +5 % RCP8.5 RCP8.5 “ CMIP5 GCMs “ Yang et al. (2017) Western Tian Shan and northern Kunlun Mountains Australia SE Australia Solid precip. -26.5% 1961–2005 to 2006– 2035 1961–2005 to 2036– 2099 “ 1986–2005 to 2080– 2099 1980–2010 to 2041– 2070 “ 1980–2010 to 2071– 2100 “ 1976–2005 to 2070– 2099 “ “ “ “ Annual precip. -5 % (high variability) RCP2.6 Downscaled GCMs Grose et al. (2015) “ “ “ “ -5 % (high variability) -5 % (high variability) RCP8.5 RCP2.6 “ “ “ “ “ Japan Tokai region “ -10 % (high variability) 1950–2005 to 2020– 2039 “ 1950–2005 to 2080– 2099 “ RCP8.5 “ “ 99th percentile of daily precip. From +10% to +50% in winter (December to February) 1984–2004 to 2080– 2100 RCP8.5 Murata et al. (2016) Central Japan Winter snowfall (November to March) Decrease in most parts of Japan (up to -300 mm) increase in the central part of northern Japan 1950–2011 to 2080– 2099 +4°C warming in 2080–2099 with respect to 1861–1880, under RCP8.5 Single dynamically downscaled GCM (MRI AGCM) MRI-AGCM3.2 (dynamically downscaled) “ “ Do Not Cite, Quote or Distribute +0.6% +3.2% SM2-16 Total pages: 87 Shafiq et al. (2019) Kawase et al. (2016) FINAL DRAFT “ Chapter 2 Supplementary Material Heavy snowfall (10 years return period) Do Not Cite, Quote or Distribute Increase (10 mm) in the inland areas of central and in northern Japan SM2-17 IPCC SR Ocean and Cryosphere “ “ Total pages: 87 “ “ FINAL DRAFT SM2.4 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Details of Studies on Snow Cover Observations and Projections Table SM2.6: Synthesis of recent studies reporting past changes in snow cover in high mountain areas, per high mountain region (as defined in Figure 2.1). SWE is snow water equivalent. Obs. stations refer to observation stations. Elevations are in meters (m) above sea level. Location Snow variable Change Time period Dataset Reference Alaska Whole area Duration Decrease 20th century Remote sensing Brown et al. (2017) “ SWE Decrease 20th century “ “ Mountainous Alaska Snow at high Increase 1840–present Indirect evidence from glacier Winski et al. (2017) elevation accumulation Western Canada and USA Western USA Springtime SWE Decrease for 92% stations 1955–present In-situ observations Mote et al. (2018) “ April 1 SWE -15 to -30% 1955 –present “ “ Western USA Annual maximum Decrease by 41% on average for 13% of 1982– 2016 Gridded product based on inZeng et al. (2018) SWE pixels situ observations Canada Duration Decrease 2 to 12 days per decade 1950– 2012 In-situ observations DeBeer et al. (2016) Iceland Whole area Duration Decrease 0 to 10 days per decade 1980–2010 Remote sensing Brown et al. (2017) Central Europe European Alps and Snow depth Decrease at low elevation, step decrease in Mid 20th In-situ, reanalyses Beniston et al. (2018) Pyrenees late 1980s century– Reid et al. (2016) present European Alps SWE Decrease at low elevation, step decrease in Mid 20th 54 obs. stations Marty et al. (2017b) late 1980s century– present European Alps Duration Insignificant trend, decrease at 700–900 m 1985–2011 Optical remote sensing Hüsler et al. (2014) in the SE and SW Alps Swiss Alps Onset date 12 days later on average 1970–2015 11 obs. stations Klein et al. (2016) “ Melt-out date 26 days earlier on average “ “ “ Austrian Alps, 500–2000 Snow cover days -13 to -18 depending on the region 1950–1979 to Modelling based on in-situ Marke et al. (2018) m 1980–2009 observations Austrian Alps, 2000– “ -12 to -14 depending on the region “ “ “ 2500 m Austrian Alps, >2500 m “ -20 (central Austria) “ “ “ French Alps, 1800 m Duration -24 days 1958–2009 Local reanalysis Durand et al. (2009) French Alps Melt onset 2 weeks earlier > 3000 m 1980–2015 In-situ observations Thibert et al. (2013) “ Melt intensity 15% stronger >3000 m “ In-situ obs. and modelling “ Pyrenees, <1000 m Snow cover duration Decrease in majority of stations 1975–2002 In-situ observations Pons et al. (2010); Beniston et al. (2018) Do Not Cite, Quote or Distribute SM2-18 Total pages: 87 FINAL DRAFT Pyrenees, >1000 m Pyrenees, Andorra, 1645 m Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere “ Number of days with snow depth above 5, 30 and 50 cm Decrease in majority of stations Increase until ~1980 then decrease (not statistically significant, high variability) 1935–2015 “ In-situ observations “ Albalat et al. (2018) Scandinavia Norway Snow depth and SWE Decrease at low elevation 20th century In-situ observations “ Northern Finland “ Snow cover duration Increase at higher elevation -2.4 days per decade 20th century 1961–2014 Southern Finland Caucasus and Middle East Central Caucasus, 2300 m North-Western Iran “ -5.7 days per decade “ “ Gridded dataset based on insitu observations “ Skaugen et al. (2012); Dyrrdal et al. (2013); Beniston et al. (2018) “ Luomaranta et al. (2019) Amount of winter snow Snow cover duration and mean snow depth Declining since late 1980s 1968–2013 In-situ observations Volodicheva et al. (2014) Decrease at most stations 1981–2011 28 in-situ observations Arkian et al. (2014) Southern Andes Whole area Snow covered area Insignificant decrease (high variability) 2000–2015 Optical remote sensing Whole area Snow covered area Decrease Passive microwave satellite 1979 2006 Low Latitudes (including tropical Andes) Compared to mid and high latitude mountain areas seasonal snow cover has limited relevance in the tropical Andes and other tropical areas, except in the immediate vicinity of glaciers. Satellite-based observations are too short to address long-term trends. High Mountain Asia Himalaya and Tibetan Snow covered area Insignificant trend (high variability 2000– 2015 Optical remote sensing Plateau compared to record length) “ Malmros et al. (2018) Le Quesne et al. (2009) Saavedra et al. (2018) Tahir et al. (2015); Gurung et al. (2017); Bolch et al. (2018); Li et al. (2018) Smith and Bookhagen (2018); Wang et al. (2018) Himalaya SWE -10.60 kg m-2 yr-1 for areas > 500 m 1987– 2009 Passive microwave remote sensing Australia SE Australia SWE Reduction, especially in springtime In-situ observations Fiddes et al. (2015); Di Luca et al. (2018) “ Duration Reduction, especially in springtime Mid-20th century– present “ “ “ Do Not Cite, Quote or Distribute SM2-19 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Table SM2.7: Synthesis of recent studies reporting 21st century projections in snow cover in high mountain areas, per high mountain region (as defined in Figure 2.1). Location Snow variable Change Time period Scenario Method Reference Alaska Mountainous SWE -10 to -30% 1970–1999 to 2040– RCP8.5 Multiple Littell et al. (2018) Alaska 2069 GCM/RCM pairs “ SWE -40 to -60% 1970–1999 to 2070– “ “ “ 2099 Western Canada and USA Western USA April 1 SWE -50% 1965–2005 to 2010– RCP8.5 M Multiple Naz et al. (2016) 2040 GCM/RCM pairs “ Duration -10 to -100 days 1976–2005 to 2071– RCP8.5 “ Musselman et al. (2018) 2100 “ Peak annual SWE -6.2 kg m-2 per 2013–2038 RCP8.5 Post-processed Fyfe et al. (2017) decade CMIP5 GCM Iceland Low elevation Snow depth -100% 1981–2000 to 2081– RCP8.5 Single RCM Gosseling (2017) 2100 Top of central Snow depth +20% 1981–2000 to 2081– “ “ “ Vatnajökull 2100 Central Europe European Alps Winter SWE <1500 m -40 % 1971–2000 to 2020– SRES A1B Multiple Steger et al. (2012); Gobiet et 2049 GCM/RCM pairs al. (2014); Beniston et al. (2018) “ “ -70% 1971–2000 to 2070– “ “ “ 2099 “ “ -10% 1971–2000 to 2020– “ “ “ 2049 “ -40% 1971–2000 to 2070– “ “ “ 2099 French Alps, 1500 Winter mean snow depth -20% 1986–2005 to 2030– RCP2.6 Adjusted multiple Verfaillie et al. (2018) m 2050 GCM/RCM pairs “ “ -30 % “ RCP8.5 “ “ “ “ -30 % 1986–2005 to 2080– RCP2.6 “ “ 2100 “ “ -80 % “ RCP8.5 “ “ European Alps Similar results as above and strengthening of the asymmetrical seasonal snow decline pattern (stronger trend for reduced Marty et al. (2017a); Terzago et snow cover duration in spring than in fall). al. (2017) Hanzer et al. (2018) Scandinavia Do Not Cite, Quote or Distribute SM2-20 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material Northern Scandinavia Duration and SWE Norway Duration Decrease at low elevation, marginal changes at high elevation -14% to -32% “ “ “ “ -15% to -50% -34% to -64% 1971–2000 to 2010– 2100 A1B GCM downscaled using RCM Räisänen and Eklund (2012); Beniston et al. (2018) 1981–2010 to 2021– 2050 “ 1981–2010 to 2071– 2100 “ RCP4.5 Scott et al. (2019) RCP8.5 RCP4.5 Adjusted multiple GCM/RCM pairs “ “ RCP8.5 “ “ -35 to 40% 1991–2000 to 2041– 2050 B2 Downscaled GCM Shkolnik et al. (2006); Sokratov et al. (2014) -13% 1980–2010 to 2035– 2065 “ “ “ 1961–1990 to 2071– 2000 “ “ “ “ “ RCP4.5 Multiple RCM López-Moreno et al. (2017) RCP8.5 RCP4.5 RCP8.5 B2 “ “ “ Vicuña et al. (2011) “ “ A2 “ “ “ “ “ Single GCM/RCM pair “ “ “ “ “ 1986–2005 to 2031– 2050 1986–2005 to 2081– 2100 1986–2005 to 2031– 2050 1986–2005 to 2081– 2100 RCP8.5 Multiple GCMs Terzago et al. (2014) “ “ “ “ “ “ “ “ “ 1980–1999 to 2030– 2049 1990–2009 to 2020– 2040 SRES A1B Multiple downscaled GCMs Multiple downscaled GCMs Hendrikx et al. (2013) “ “ Caucasus and Middle East West Caucasus, Snow cover duration 567 m Southern Andes Whole area Mean SWE -38% to -89% “ “ “ Limarí river basin, north-central Chile “ “ “ “ “ High Mountain Asia Hindu Kush and Karakoram “ “ Duration “ Peak SWE (> 5000m) -17% 7 days 10 days -32 % “ ; 2500–3000 m “ ; 2000–2500 m Peak SWE (> 5000m) “ ; 2500–3000 m “ ; 2000–2500 m -82% -100% -41 % -96 % -100 % Winter snow depth (December to April) “ -7 % Himalaya “ -25 % “ “ -55% New Zealand and Australia Australia SWE Australia SWE Do Not Cite, Quote or Distribute IPCC SR Ocean and Cryosphere -28 % Reduction, especially below 1000 m -15 % SM2-21 SRES A2 Total pages: 87 “ “ “ “ “ “ “ Di Luca et al. (2018) FINAL DRAFT Chapter 2 Supplementary Material “ “ -60 % New Zealand SWE; 1000 m -3% to -44 % “ “ “; 2000 m “; 1000 m -8 % to -22 % -32% to -79% “ Japan Japan “; 2000 m -6% to -51 % Winter snow depth, low elevation -50 % “ mountain catchment “; high elevation SWE -10 % -36% Do Not Cite, Quote or Distribute SM2-22 IPCC SR Ocean and Cryosphere 1990–2009 to 2060– 2080 1980–1999 to 2030– 2049 “ 1980–1999 to 2080– 2099 “ “ “ “ SRES A1B Hendrikx et al. (2012) “ “ Multiple downscaled GCMs “ “ “ “ “ Base: 1990s Future: time period corresponding to 2°C warming. “ 1981–2000 to 2046– 2065 +2°C global warming (from SRES A1B) “ SRES A1B Multiple downscaled GCMs (time sampling) “ Multiple downscaled GCMs Katsuyama et al. (2017) Total pages: 87 “ “ “ Bhatti et al. (2016) FINAL DRAFT SM2.5 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Details on Climate Models used in Figure 2.3 Table SM2.8: List of CMIP5 General Circulation Models (GCM) and where available, Regional Climate Models (RCM) used for projecting the winter and summer air temperature (T) and snow water equivalent (SWE), for RCP2.6 and RCP8.5, for the five regions represented in Figure 2.3: Rocky Mountains in North America, Subtropical Central Andes, European Alps, Hindu Kush and Karakoram, and Himalaya. For the Rocky Mountains, Hindu Kush and Karakoram, and Himalaya only RCP8.5 data were used. Rocky Mountains GCM (default is r1i1p1) RCM (driven by corresponding GCM) Subtropical Central Andes RCP8.5 T SWE RCP2.6 T SWE European Alps RCP8.5 T SWE Hindu Kush and Karakoram; Himalaya RCP2.6 RCP8.5 T T SWE SWE RCP8.5 T ACCESS1-0 X X ACCESS1-3 X X X X Bcc-csm1-1 X BNU-ESM X CanESM2 X CCCma-CanRCM4 X X UQAM-CRCM5 X X CCSM4 X X CESM1-BGC X X X X CESM1-CAM5 X X CMCC-CM X X X X X X X X CLMcom-CCLM4-8-17 Do Not Cite, Quote or Distribute SM2-23 X X X CNRM-CM5 SWE X X Total pages: 87 X FINAL DRAFT Chapter 2 Supplementary Material Rocky Mountains IPCC SR Ocean and Cryosphere Subtropical Central Andes CNRM-ALADIN53 European Alps X SMHI-RCA4 X Hindu Kush and Karakoram; Himalaya X X CSIRO-Mk3-6-0 X EC-Earth (r8i1p1) X EC-EARTH X X FGOALS-g2 X GFDL-CM3 X GFDL-ESM2G X NCAR-WRF X X GISS-E2-R X HadGEM2-CC X HadGEM2-ES X NCAR-WRF X X X X CLMcom-CCLM4-8-17 X SMHI-RCA4 X CLMcom-CCLM4-8-17 X X ICHEC-EC-EARTH (r12i1p1) SMHI-RCA4 Do Not Cite, Quote or Distribute X SM2-24 Total pages: 87 X X FINAL DRAFT Chapter 2 Supplementary Material Rocky Mountains IPCC SR Ocean and Cryosphere Subtropical Central Andes European Alps Hindu Kush and Karakoram; Himalaya ICHEC-EC-EARTH (r3i1p1) DMI-HIRHAM5 X X IPSL-CM5A-LR X IPSL-CM5A-MR X SMHI-RCA X IPSL-CM5B-LR X MIROC5 X X X MIROC-ESM-CHEM X MIROC-ESM X MRI-CGCM3 X X X X X MPI-M-MPI-ESM-LR NCAR-WRF X X UQAM-CRCM5 X X CLMcom-CCLM4-8-17 MPI-CSC-REMO2009 X X SMHI-RCA4 X X X X X MPI-M-MPI-ESM-LR (r2i1p1) MPI-CSC-REMO2009 Do Not Cite, Quote or Distribute X SM2-25 Total pages: 87 X X X FINAL DRAFT Chapter 2 Supplementary Material Rocky Mountains IPCC SR Ocean and Cryosphere Subtropical Central Andes European Alps Hindu Kush and Karakoram; Himalaya MPI-M-MPI-ESM-MR UQAM-CRCM5 X X MRI-ESM1 X X NorESM1-M X Ensemble members Do Not Cite, Quote or Distribute 7 SM2-26 7 8 4 14 5 5 Total pages: 87 2 13 7 23 3 FINAL DRAFT SM2.6 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Synthesis of Recent Studies Reporting on Past and Projected Changes of River Runoff Table SM2.9: Synthesis of recent studies reporting on past and projected changes in river runoff, per high mountain region (as defined in Figure 2.1). Entries per region are sorted according to increasing percentage of glacier cover for past and projected changes separately. Note that studies on annual runoff that are listed in Table SM2.9 are not listed here. The year of peak water given there indicates the year before which annual runoff is increasing and beyond which it is decreasing. Location Basin area (% Variable Cause Time period Method Scenario Reference glacier cover) (change) Global-scale 97 snow (glacier melt not Spring-summer Transition of snowfall 1955–2005 Model, 19 RCP8.5 Mankin et al. (2015) sensitive basins considered in snowmelt runoff to rainfall to 2006– GCMs in 421 basins in model) (decrease) 2080 northern hemisphere Alaska Gulf of Alaska 420,300 km2 Annual runoff Increased glacier melt 1980–2014 Model Past Beamer et al. (2016) (17 %) (+1-2 km3 yr-1) Gulkana, 24.6 km2 and Summer Runoff Increased glacier melt 1966–2011 2 stream Past O’Neel et al. (2014) Wolverine 31.5 km2 (>50%) (increase) gauges Gulf of Alaska 420,300 km2 Annual runoff Increased glacier melt 1984–2014 Downscaled RCP4.5 RCP8.5 Beamer et al. (2016) (+25–46%) to 2070– GCMs 2099 “ “ Dec.–Feb. runoff Transition of snowfall “ “ “ “ (+93–201%) to rainfall “ “ Spring peak Earlier snowmelt “ “ “ “ (1month earlier) Western Canada and USA South and 0.1–19 % August runoff Decreased snow and 1975–2012 20 stream Past Brahney et al. (2017) Central (decrease) glacier melt gauges, Columbia Basin hydro-graph separation Canadian Rocky 166–1,170 km2 Summer runoff Decreased glacier 1955–2010, 6 stream Past Fleming and Dahlke (2014) Mountains and (0–23.4%), no (decrease in melt, decreased depending on gauges adjacent ranges data in some glacierized precipitation sites basins basins) Bridge river, 139 km2 Winter runoff Increased glacier melt 1979–2014 stream gauge Past Moyer et al. (2016) British Columbia (52.6% in 2014) (increase) (Canada) “ “ Summer runoff Decreased glacier melt “ “ “ “ (decrease) Do Not Cite, Quote or Distribute SM2-27 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material Sierra Nevada, northeast of California (USA) “ 4,781 km2 (0 %) Winter runoff (~+19%) “ Athabasca (Canada) 161,000 km2 (0 %) Spring peak (1 month early) Summer runoff (+6-76 %) “ “ Whole USA (not significant) “ “ Western North America (not significant) “ “ “ “ Western USA (not significant) British Columbia 0-8% “ IPCC SR Ocean and Cryosphere Transition of snowfall to rainfall, increased precipitation Earlier snowmelt 1964–2014 to 2015– 2064 “ 7 GCMs RCP4.5, RCP8.5 Sultana and Choi (2018) “ “ “ Increased snowmelt, increased precipitation 1983–2013 to 2061– 2100 “ Downscaled 1 GCM RCP4.5 RCP8.5 Shrestha et al. (2017) “ “ “ 1961–2005 to 2011– 2050 Downscaled 10 GCMs RCP8.5 Naz et al. (2016) Earlier snowmelt “ “ “ “ Transition of snowfall to rainfall downscaled 10 GCMs RCP8.5 Pagán et al. (2016) “ “ “ Winter runoff (+3–114%) Winter runoff (increase in snow-dominated basins) Spring peak (earlier in snowdominated basins) Winter runoff (increase) Transition of snowfall to rainfall Transition of snowfall to rainfall Summer runoff (decrease) Spring peak (611 days earlier) Spring peak (1.5–4 weeks early) Winter runoff (+45–95 %) Decreased snowmelt 1965–2005 to 2010– 2050 “ Earlier snowmelt “ “ “ “ Earlier snowmelt downscaled 10 GCMs RCP4.5, RCP8.5 Li et al. (2017) downscaled 8 GCMs SRES B1, A1B Schnorbus et al. (2014) “ Summer runoff (-58% to -9%) “ “ “ Nooksack (USA) 2,000 km2 (< 1 %) Winter runoff (+39–88 %) Decreased snowmelt, transition of snowfall to rainfall Transition of snowfall to rainfall 1960–2005 to 2080– 2100 1961–1990 to 2041– 2070 “ downscaled 3 GCMs SRES A2, B1 Dickerson-Lange and Mitchell (2014) “ “ Decreased snowmelt “ “ “ “ “ Summer runoff (-50% to -26 %) Spring peak 1950–1999 to 2060– 2090 “ Earlier snowmelt “ “ “ “ Do Not Cite, Quote or Distribute Increased snowmelt, increased rainfall SM2-28 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material (1 month early) Annual peak (increase, 1 month later) Winter runoff (increase) “ “ Fraser, N. America 240,000 km2 (1.5 %) “ “ Summer runoff (decrease) “ “ Annual peak (20-30 days earlier) (some including glaciers ) Winter runoff (increase in glacier- or snowdominated basins) Spring peak (earlier) Winter runoff (increase at > 1800 m a.s.l.) Summer runoff (decrease) Central Europe Alps “ “ Alps, (northern Italy) “ ~100–10,000 km2 (some including glaciers ) “ Western Austria (0–71.9 %) Middle and upper Rhine 144,231 km2 (<1%) “ “ Do Not Cite, Quote or Distribute Annual flow (increase at high elevations, decrease at low elevations) Winter runoff (+4-51%) Summer runoff (-40% to -9%) Decreased snowmelt, increased extreme precipitation Transition of snowfall to rainfall IPCC SR Ocean and Cryosphere “ “ “ “ 1980–2009 to 2040– 2069 “ downscaled 12 GCMs RCP4.5 RCP8.5 Islam et al. (2017) “ “ “ “ “ “ “ Transition of snowfall to rainfall 1961–2005 177 stream gauges Past Bard et al. (2015) Earlier snowmelt and glacier melt Transition of snowfall to rainfall “ “ “ “ 1921–2011 23 stream gauges Past Bocchiola (2014) Decreased snowmelt and glacier melt, increased evapotranspiration Increased and decreased glacier melt “ “ “ “ 1980–2010 32 steam gauges Past Kormann et al. (2015b) Transition of snowfall to rainfall, earlier snowmelt 1979–2008 to 2021– 2050 and 2070– 2099 “ 10 GCMRCMs SRES A1B Bosshard et al. (2014) “ “ “ Decreased snowmelt, transition of snowfall to rainfall Earlier snowmelt Decreased snowmelt SM2-29 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material Gigerwaldsee (Switzerland) 97 km2 (<1%) Summer runoff (decrease) Decreased glacier melt Swiss Alps 20–1,577 km2 (0-4%) Summer runoff (-32 to -56%) Swiss Alps 231–1,696 km2 (0–22 %) Winter runoff (increase at high elevations) Transition of snowfall to rainfall, Earlier snowmelt Transition of snowfall to rainfall European Alps Glacierized European Alps Annual runoff (decrease) Decreased glacier melt “ “ Decreased glacier melt Alps, Po (Italy) 71,000 km2 (small) Summer runoff (decrease) Winter runoff (increase) “ “ Earlier snowmelt Canton Graubünden “ 7,214 km2 (2.4%, ~20% in high elevation catchments) “ Spring peak (1 month earlier) Winter runoff (increase) “ “ Decreased snowmelt, decreased precipitation Earlier snowmelt Göscheneralpsee, Dammareuss subcatchment (central Switzerland) Findelen, Swiss Alps “ 95 km2 (20%), 10 km2 (50%) Summer runoff (decrease) Spring peak (earlier) Summer runoff (decrease) Annual runoff (decrease) Spring peak (earlier) 21.18 km2 (70%) “ Do Not Cite, Quote or Distribute IPCC SR Ocean and Cryosphere 1992–2021 to 2035– 2064 and 2069–2098 1980–2009 to 2070– 2099 1980–2009 to 2020– 2049, 2045– 2074, 2070– 2099 1980–2009 to 2010– 2039, 2040– 2069, 2070– 2099 “ 7 GCMRCMs SRES A1B Etter et al. (2017) 10 GCMRCMs SRES A1B Jenicek et al. (2018) 10 GCMRCMs RCP2.6, SRES A1B, A2 Addor et al. (2014) 4 GCMs RCP2.6, RCP4.5, RCP8.5 Farinotti et al. (2016) “ “ “ 1960–1990 to 2020– 2050 “ 2 RCMs SRES A1B Coppola et al. (2014) “ “ “ 2000–2010 to 2021– 2050, 2070– 2095 “ 10 RCMs SRES A1B Bavay et al. (2013) “ “ “ “ “ “ “ Decreased snow melt, decreased glacier melt 1981–2010 to 2021– 2050, 2070– 2099 10 RCMs SRES A1B Kobierska et al. (2013) Decreased glacier melt 1976–2086 1 RCM SRES A2 Uhlmann et al. (2013) Earlier snowmelt “ “ “ “ Transition of snowfall to rainfall Transition of snowfall to rainfall SM2-30 Total pages: 87 FINAL DRAFT Scandinavia Arctic coastal Norway Chapter 2 Supplementary Material “ 56-422 km2 (0– 34.9%), no data in some basins “ Whole Scandinavia (including glaciers) “ “ Caucasus and Middle East Eastern Anatolia (0%) (Turkey) “ “ Euphrates-Tigris 880,000 km2 (0%) Low Latitudes (tropical Andes) La Paz (Bolivia) 18-78 km2 (5–12%) Winter runoff (increase) Transition of snowfall to rainfall Summer runoff (decrease basins including glaciers) Winter runoff increase ~40%, excl. southern Sweden and Denmark) Summer runoff (decrease ~40%) Decreased glacier melt 1955–2010, depending on sites “ 7 stream gauges Past Fleming and Dahlke (2014) “ “ “ Transition of snowfall to rainfall 1980–2009 to 2041– 2070 6 GCMRCMs SRES A1B Räty et al. (2017) Decreased snowmelt, increased evapotranspiration “ “ “ “ Snowmelt peak (~1 week earlier) Snowmelt peak (~4 week earlier) Earlier snowmelt 1970–2010 Past Yucel et al. (2015) Earlier snowmelt SRES A2 “ Snowmelt peak (18–39 days earlier) Earlier snowmelt 1961–1990 to 2070– 2099 1961–1990 to 2041– 2070, 2071– 2099 15 stream gauges singe GCMRCM 3GCM-RCMs SRES A1F1, A2, B1 Bozkurt and Sen (2013) Annual runoff (no significant change) Annual runoff (-4% and -24% in later period) Decreased ice melt compensated by increased precipitation Decreased glacier melt 4 stream gauges and model 11 downscaled GCMs Past Soruco et al. (2015) RCP4.5 Frans et al. (2015) “ “ “ 4 stream gauges Past Balocchi et al. (2017) Zongo (Bolivia) 3 km2 (35 % in 1987) “ “ Wet season runoff (increase) Transition of snowfall to rainfall 222-3,572 km2 (7.02 km2 in total) Annual runoff (no significant change) Decreased glacier melt compensated by increased precipitation Southern Andes Elqui (Chile) Do Not Cite, Quote or Distribute IPCC SR Ocean and Cryosphere SM2-31 1963–1007 1987–2010 to 2030– 2050, 2080– 2100 “ 1970–2009 Total pages: 87 FINAL DRAFT Rio del Yeso (Andes of central Chile) Juncal (Chile) Chapter 2 Supplementary Material 62 km2 (19%) Annual runoff (decrease) Decreased snowmelt 2000–2015 Model Past Burger et al. (2019) (including glaciers ) Seasonal runoff peak (1month early) Earlier snowmelt, transition of snowfall to rainfall 2001–2010 to 2041– 2050, 2051– 2060, 2060– 2100 12 GCMs RCP4.5, RCP8.5 Ragettli et al. (2016) Spring and summer runoff (increase) Increased snowmelt, transition of snowfall to rainfall 1970–2005 stream gauge Past Reggiani and Rientjes (2015) Spring and Summer runoff (decrease) Spring and autumn runoff (Increase) Decreased glacier melt “ “ “ “ Increased snowmelt and ice melt 1965–2007 2 stream gauges Past Kriegel et al. (2013) Winter-early spring runoff (increase) Annual runoff (increase for higher fraction of glacier area) Winter-spring runoff (increased, earlier) Increased snowmelt, transition of snowfall to rainfall Increased ice melt “ “ “ “ 1960–2014 23 stream gauges Past Chen et al. (2016) Earlier snow and glacier melt 1961–2008, depending on site 4 stream gauges Past Shen et al. (2018) Summer runoff (increase) Summer runoff (increase) June and July runoff (increase and turn to decrease from 2000 to 2010) Increased ice melt, increased precipitation Increased ice melt 1957–2004 Model Past Duethmann et al. (2015) “ “ “ “ Decreased snowmelt 1985–2010 Stream gauges, hydrograph separation Past Mukhopadhyay and Khan (2014) High Mountain Asia Astore, Gilgit, 3,750 km2, Katchura, (upper 12,800 km2, 115,289 km2, Indus) (not significant) Hunza, (upper 13,925 km2, Indus) (including glaciers) Naryn (Tien 3,879 km2 (10% Shan) in 1970s) and 5,547 km2 (12% in 1970s) “ “ Tien Shan (including glacier ) Toxkan, Kunmalik, Kaidu, Huangshuigou (Tien Shan) Kakshaal and, Tarim Sari-Djaz, Tarim 4,298–19,166 km2 (including glaciers ) Shigar (Karakoram) IPCC SR Ocean and Cryosphere 18,410 km2 (4.4%) 12,948 km2 (20.9%) 7,040 km2 (30%) Do Not Cite, Quote or Distribute SM2-32 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material “ “ Chhota Shigri (Western Himalaya) ~35 km2 (46.5%) Sikeshu (Tien Shan) Upper Indus 921 km2 (37%) ~425,000 km2 (5%) “ “ “ “ Chu (Tien Shan) 9,548 km2 (2-7%) “ “ Upper basin of Indus, Brahmaputra, Ganges, Salween, Mekong Naryn (Tien Shan) (0.2–5.4%) IPCC SR Ocean and Cryosphere August runoff (increase) Summer runoff (+14-22%) Increased glacier melt “ “ “ “ Increased glacier melt RCM and mass-balance model Past Engelhardt et al. (2017) Annual runoff (increase) June and July runoff in lower elevations (decrease) Winter runoff in lower elevation (increase) Spring peak (earlier) Annual runoff (-27.7% to 6.6%) Increased glacier melt 1955–1969 to 1970– 1984, 1985– 1999, 2000– 2014 1964–2004 1 stream gauge 4 GCMRCMs Past Wang et al. (2015) RCP4.5, RCP8.5 Lutz et al. (2016a) Spring peak (decrease, 1 month earlier) Spring peak (decrease, earlier) Decreased glacier melt, earlier snowmelt 58,205 km2 (2%) “ “ Decreased snowmelt, decreased precipitation 1971–2000 to 2071– 2100 Increased precipitation, transition of snowfall to rainfall Earlier snow and glacier melt Decreased glacier melt “ “ “ “ “ “ “ “ 1966–1995 to 2016– 2045, 2066– 2095 “ 5 GCMs RCP2.6, RCP4.5, RCP8.5 Ma et al. (2015) “ “ “ Earlier snowmelt, transition of snowfall to rainfall 1998–2007 to 2041– 2050 4 GCMs RCP4.5, RCP8.5 Lutz et al. (2014) Annual runoff (decrease) Decreased precipitation, decreased snowmelt 5 GCMs RCP2.6, RCP4.5, RCP8.5 Gan et al. (2015) “ Winter runoff (-2.2 to +19.8%) “ “ “ “ Spring peak (1 month earlier) Decreased precipitation, decreased snowmelt Earlier snowmelt 1966–1995 to 2016– 2045, 2066– 2095 “ “ “ “ “ Do Not Cite, Quote or Distribute SM2-33 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material Chon Kemin (Kyrgyz-Kazakh region) 1,037 km2 (11%) Summer runoff (-15 to -4%, -66 to -9%) Decreased ice melt “ “ Beida River, upper Heihe (China) Lhasa, upper Brahmaputra 565–6,706 km2 (total 318.2 km2) Spring runoff (+7 to +23%, +18 to +62%) Annual runoff (increase) Increased winter precipitation, increased snowmelt Increased glacier melt Early summer runoff (decrease) Koshi (Nepal) 32,800 km2 (2% in 1970, 1.3– 11.5% for selected subbasins) 3,712 km2 (13%) Upper Langtang (Himalaya) IPCC SR Ocean and Cryosphere 1955–1999 to 2000– 2049, 2050– 2099 “ 4 GCMs RCP2.6, RCP8.5 Sorg et al. (2014a) “ “ “ 1957–2013 3 stream gauges Past Wang et al. (2017b) Decreased snowmelt, increased evapotranspiration 1971–2000 to 2011– 2040 and 2051–2080 single GCMRCM SRES A1B, A2, B2 Prasch et al. (2013) Summer runoff (decrease) Decreased snow melt 5 GCMRCMs SRES A1B Nepal (2016) (including glaciers) Peak runoff (increase) Transition of snowfall to rainfall 12 GCMs RCP4.5, RCP8.5 Ragettli et al. (2016) Langtang (Himalaya) 360 km2 (46%) Annual runoff (increase) Increased glacier melt 2000–2010 to 2040– 2050, 2086– 2096 2001–2010 to 2041– 2050, 2051– 2060, 2060– 2100 1961–1990 to 2021– 2050, 2071– 2100 RCP4.5, RCP8.5 8 GCM Immerzeel et al. (2013) Baltoro 1,415 km2 (46%) ~35 km2 (46.5%) Annual runoff (increase) Spring-summer runoff (increase) Summer runoff (decrease) Spring runoff (increase, earlier in 2 GCMs, decrease in 1 GCM) Increased glacier glacier melt Earlier snow and glacier melt “ “ “ 1951–2099 to 2070– 2099 “ GCM-RCM RCP4.5, RCP8.5 Engelhardt et al. (2017) “ “ “ 1980–2010 to 2030– 2059, 2070– 2099 3 GCMs RCP2.6, RCP8.5 Garee et al. (2017) Chhota Shigri (Western Himalaya) “ Hunza, upper Indus (Western Himalaya) “ 13,567 km2 (including glaciers) Do Not Cite, Quote or Distribute Decreased glacier melt Early snow melt SM2-34 Total pages: 87 FINAL DRAFT “ Chapter 2 Supplementary Material “ New Zealand and SE Australia Upper Waitaki 9,490 km2 (New Zealand) (including glaciers) “ Summer runoff (decrease in 2 GCMs, slight increase in 1 GCM) Decreased glacier melt “ “ “ “ Late winterspring runoff (increase) Transition of snowfall to rainfall 1980–1999 to 2030– 2049, 2030– 2049, 2080– 2099 “ Downscaled 12 GCMs SRES A1B Caruso et al. (2017) “ “ “ 1960–1991 to 2010– 2039, 2030– 2059, 2070– 2099 2046–2065 11 RCMs SRES A1F1, A1B, B1 Capell et al. (2014) 5 GCMs SRES A1B Bhatti et al. (2016) Summer runoff (decrease) Other regions (affected by snow cover but lacking glaciers) Eastern Scotland 749 km2 Winter runoff (0%) (increase) Shubuto, Hokkaido (Japan) “ 367.1 km2 (0%) Do Not Cite, Quote or Distribute IPCC SR Ocean and Cryosphere Spring peak (~14 days earlier) Decreased snowmelt, decreased precipitation Transition of snowfall to rainfall, precipitation increase Earlier snowmelt SM2-35 Total pages: 87 FINAL DRAFT SM2.7 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Details of Studies on Peak Water Table SM2.10: Overview of studies providing estimates of the timing of peak water for the individual glaciers or glacier-fed river basins plotted in Figure 2.6. Peak water is the approximate year derived from observations or modelling (past) and modelling (future) when on average annual runoff reaches a maximum due to glacier shrinkage. Years are approximated from the information presented in each study, and in some cases represent an average of results from different scenarios (see remarks). Local refers to estimates for individual glaciers (no matter glacier area) and river basins with multiple glaciers but total glacier cover less than 150 km2. All other estimates are referred to as regional. Glacier area refers to reported area typically referring to the beginning of the study period. Glacier cover refers to the glacier area in percent of the river basin’s area. Glacier/basin name Domain type Peak water Glacier area Glacier cover Reference Remarks; scenario (if reported) (%) (year) (km2) Alaska Copper River basin regional ~2070 ~13,000 ~21 Valentin et al. (2018) RCP4.5 Wolverine local ~2050 17 67 Van Tiel et al. (2018) No clear peak; RCP4.5 Wolverine local ~2035 17 67 No clear peak; RCP8.5 Western Canada Hood local ~2015 ~9 100 Frans et al. (2016) Runoff from glacier area Moyer et al. (2016) Qualitative statement: At / close to peak Bridge local ~2015 73 53 water Mica basin regional ~2000 1,080 52 Jost et al. (2012) Already past peak water; year not reported Bridge local ~2000 73 53 Stahl et al. (2008) Already past peak water; year not reported Hoh local 1988 18 100 Frans et al. (2018) Runoff from glacier area; RCP4.5 Stehekin local 1985 19 100 Cascade local 1984 12 100 Hood local 1995 5 100 Thunder local 2040 32 100 Nisqually local 2053 18 100 Several basins in Western Fleming and Dahlke (2014) “Peak Water already over” (qualitative regional ~2000 150 Canada statement); runoff data analysis Clarke et al. (2015) Runoff from glacier area; Peak water varying Western Canada, coastal regional ~2035 26,700 100 between ~2023 and 2055; RCP2.6 Alaska Western Canada, coastal Alaska regional ~2042 26,700 100 local/ regional ~2055 ~5000 100 2020 5 49 Runoff from glacier area; Peak water varying between ~2024 and 2065; RCP8.5 Iceland Southern Vatnajökull, Langjökull, Hofsjökull Björnsson and Pálsson (2008) Central Europe (European Alps) Gries local Do Not Cite, Quote or Distribute SM2-36 Farinotti et al. (2012) Total pages: 87 A1B FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Silvretta Rhone Gorner Aletsch Trift Zinal Moming Weisshorn Morteratsch Forno Albigna Plaine Morte Findel local local local local local local local local local local local local local 2015 2042 2035 2050 2045 2047 2039 2035 2020 2042 2020 2055 2035 5 18 51 117 17 11 6 3 16 7 6 8 16 5 46 63 59 43 65 63 39 15 34 30 100 74 Findel local ~2050 16 74 local (>100 glaciers) 1997 2000 2004 <0.05 0.05–0.125 0.125–0.5 100 100 100 Huss and Fischer (2016) regional regional regional regional ~2045 ~2025 ~2070 ~2070 112 112 ~30,000 ~30,000 11 11 Sorg et al. (2014a) Hailuogou local ~2050 45 36 Hailuogou Kakshaal basin local regional ~2070 ~2018 45 740 36 4 Sari-Djaz basin regional ~2033 2,580 20 Naryn basin Naryn basin Naryn basin Urumqi Yangbajing basin Headwaters of Brahmaputra, Ganges, Indus All High-Mountain Asia glaciers regional regional regional local regional ~2020 ~2030 ~2050 2020 ~2025 1,160 1,160 1,160 2 312 2 2 2 52 11 regional ~2050 ~30,000 regional ~2030 ~90,000 Swiss Alps Swiss Alps Swiss Alps High Mountain Asia Chon Kemin basin Chon Kemin basin Largest rivers of China Largest rivers of China Do Not Cite, Quote or Distribute SM2-37 Huss et al. (2008) A1B Huss et al. (2010) A1B Reynard et al. (2014) Uhlmann et al. (2013) Huss et al. (2014) A1B Gao et al. (2018) Prasch et al. (2013) Lutz et al. (2014) RCP2.6 RCP8.5 Peak water unclear from study; RCP2.6 Peak water unclear from study; RCP8.5 No clear peak; declining glacier runoff after 2050; RCP4.5 RCP8.5 Runoff from glacier area; aggregate of different emission scenarios; RCP2.6/RCP8.5 RCP2.6 RCP4.5 RCP8.5 RCP4.5 Peak water between 2011 and 2040; A1B RCP4.5 Kraaijenbrink et al. (2017) RCP4.5 Su et al. (2016) 100 A1B (Peak water 2035–2065 depending on climate model Zhang et al. (2015) Duethmann et al. (2016) Gan et al. (2015) Total pages: 87 FINAL DRAFT All High-Mountain Asia glaciers Chhota Shigri Chhota Shigri Hypothetical Hypothetical Langtang Baltoro Langtang Baltoro Langtang Langtang Low Latitudes (Andes) Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere regional ~2050 ~90,000 100 local local local local local local local local local local 2040 2020 2055 2064 2045 2048 2044 2065 ~2055 ~2070 16 16 50 50 120 520 120 520 120 120 46 46 1 1 100 100 100 100 34 34 Rio Santa basin regional ~2005 200 2 Zongo local 2010 3 21 Cordillera Blanca regional ~1995 480 ~1990 200 Sub-basins of Rio Santa Scandinavia Nigardsbreen Nigardsbreen Southern Andes Juncal Juncal local local ~2080 ~2080 local local 2030 2020 Do Not Cite, Quote or Distribute SM2-38 45 45 34 34 RCP8.5 Engelhardt et al. (2017) Rees and Collins (2006) Immerzeel et al. (2013) Ragettli et al. (2016) Carey et al. (2014) Frans et al. (2015) Polk et al. (2017) 2 Baraer et al. (2012) 70 70 Van Tiel et al. (2018) 14 14 Ragettli et al. (2016) Total pages: 87 No clear peak; RCP4.5 No clear peak; RCP8.5 Runoff from glacier area RCP4.5 RCP8.5 RCP4.5 RCP8.5 RCP4.5 RCP8.5 “Peak water already over” (qualitative statement) “Peak water already over” (qualitative statement) Analysis of observations No clear peak; RCP4.5 No clear peak; RCP8.5 RCP4.5 RCP8.5 FINAL DRAFT SM2.8 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Details of Studies on Observed Impacts Attributed to Cryosphere Changes Table SM2.11: Overview of studies documenting observed impacts on ecosystems, other natural systems and human systems over the past several decades that can at least partly be attributed to changes in the cryosphere, per high mountain region (as defined in Figure 2.1). Other additional climatic or non-climatic drivers are not listed. Confidence levels refer to confidence in attributing the impact to cryosphere changes (H for high, M for medium). Only studies where the confidence in attribution to cryosphere change is at least medium are listed. Also listed whether or not the impact is positive (pos), neg (neg) or mixed for the impacted system. Figure 2.8 is based on the data provided in this table. Location Affected Impact Cryosphere Change Attribution Positive/Ne Reference Sector or Confidence gative/Mix System ed Alaska Increase in frequency of large rock Alaska Landslides Permafrost degradation M neg Coe et al. (2017) avalanches Terrestrial Population performance of a large van de Kerk et al. Alaska Spring snow cover M mixed ecosystems mammal (dall sheep) (2018) (tundra) Terrestrial Decline in abundance & offspring Harsh winter conditions (extreme Rattenbury et al. ecosystems Alaska M neg recruitment of a large mammal weather events); delayed spring onset / (2018) (tundra; (mountain goat) end of snow season forest) Culture, Route change for Iditarod dog-sled Insufficient snow cover, lack of Alaska H neg Hagenstad et al. (2018) Tourism race river/lake ice. Western Canada and USA Reduction in peak winter snow H (snow) Jost et al. (2012); Jost British Columbia Hydropower Change in runoff timing mixed accumulation, glacier decline. M (glacier) and Weber (2013) Sacramento River Reduced snow pack due to more Hydropower Change in runoff timing H neg Reclamation (2014) basin, California precipitation as rain. San Joaquin River Reduced snow pack due to more Hydropower Change in runoff timing M neg Reclamation (2014) basin, California precipitation as rain. Upper Colorado River, Kopytkovskiy et al. Hydropower Change in runoff timing Earlier snowmelt runoff H neg USA (2015) Reduction in dry season stream flow due Cascades Agriculture Irrigation M neg Frans et al. (2016) to glacier retreat Rocky Reduction in summer stream flow Agriculture Irrigation M neg McNeeley (2017) Mountains/Cascades because of reduced snowpack British Columbia Landslides Increase in landslide frequency Glacier retreat and loss M neg Cloutier et al. (2017) Decrease in frequency of rain-onDecrease in duration and depth of snow Entire Western USA Floods M pos McCabe et al. (2007) snow flood event at lower elevation cover Increase in frequency of rain-onIncrease in frequency of rainfall at high Entire Western USA Floods M neg “ snow flood event at higher elevation elevation in winter. Do Not Cite, Quote or Distribute SM2-39 Total pages: 87 FINAL DRAFT Location Canada Colorado Rocky Mountains Mid-elevation Northern Rocky Mountains Colorado Rocky Mountains Cascade Mountains Colorado Rocky Mountains Northern Rocky Mountains, Montana Montana Rocky Mountains Chapter 2 Supplementary Material Affected Sector or System Terrestrial ecosystems (tundra; forest) Terrestrial ecosystems (tundra) Terrestrial ecosystems (forest) Terrestrial ecosystems (tundra) Terrestrial ecosystems (tundra) Terrestrial ecosystems (subalpine meadows) Terrestrial ecosystems (forest) Freshwater ecosystems Freshwater ecosystems W. USA and W. Canada Tourism Cascades, USA Tourism Iceland Sandá í Þistilfirð, Iceland Hydropower Do Not Cite, Quote or Distribute IPCC SR Ocean and Cryosphere Impact Cryosphere Change Attribution Confidence Positive/Ne gative/Mix ed Reference Population dynamics of a large mammal (wolverine) Winter snowpack decline, negatively correlated with temperature anomalies H mixed Brodie and Post (2010) Changes in vegetation distribution (shrub and tundra expansion) Spring snow cover (snow water equivalent) M pos Bueno de Mesquita et al. (2018) Fire extent, fire season severity, and fire season duration increase Earlier spring snow-melt M neg Westerling (2016) Snow changes M mixed Suding et al. (2015) Change in abundance of a small mammal (pika) at different elevations Record low snowpack (snow drought) H mixed Johnston et al. (2019) Decrease in peak season net ecosystem production Earlier snowmelt, longer early season drought M neg Sloat et al. (2015) Reduced survival of a small mammal (snowshoe hare) due to camouflage mismatch Snow cover duration M neg Zimova et al. (2018) M neg Giersch et al. (2017) Muhlfeld et al. (2011) M neg Young et al. (2018) Less snow H neg Steiger et al. (2017); Hagenstad et al. (2018) Glacier retreat M neg Orlove et al. (2019) Change in seasonality of snowmelt M neg Einarsson and Jónsson (2010) Changing upper and lower boundaries of alpine tundra, and within plant community shifts Loss of endemic invertebrates Cutthroat trout and bull trout range reduced Reduced operating capabilities of ski resorts Reduced ice-climbing opportunities and reduced attractions for summer trekking Change in timing of input SM2-40 Decreased glacier runoff due to glacier decline Decreased glacier runoff due to glacier decline Total pages: 87 FINAL DRAFT Location Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Affected Sector or System Impact Cryosphere Change Attribution Confidence Positive/Ne gative/Mix ed Austari-Jökulsá, Iceland Hydropower Change in timing of input Northern Iceland Landslides Iceland Jokulsarlon Reference Change in seasonality of snowmelt and glacier decline M neg Large debris slide Deep thawing of ground ice H neg Freshwater ecosystems Change in species interactions and loss of taxa Decreased runoff due to glacier decline M neg Milner et al. (2017) Tourism Glacier-based tourism Positive effect - picturesque glacial lagoon formed by glacier retreat H pos Þórhallsdóttir and Ólafsson (2017) M neg Thies et al. (2007) M neg Ilyashuk et al. (2018) M neg Thies et al. (2013) M neg Alberton et al. (2017) M pos Hänggi et al. (2011); Hänggi and Weingartner (2011) M mixed “ M neg Weingartner et al. (2013) M - “ M pos “ M neg M pos “ Hänggi et al. (2011); Hänggi and Weingartner (2011) Einarsson and Jónsson (2010) Sæmundsson et al. (2018) Central Europe Increased heavy metal concentrations in lakes Increased heavy metal concentrations in lakes Increased heavy metal concentrations in streams Release of solutes from thawing permafrost Release of solutes from thawing permafrost Release of solutes from thawing permafrost Reduction of perennial snowpacks and earlier snowmelt - reduced input and change in seasonality of input European Alps Water quality European Alps Water quality European Alps Water quality Carpathians, Eastern Europe Hydropower Reduced water inflow in input due to change in runoff timing Löntsch, Switzerland Hydropower Increase in runoff (short-term) Löntsch, Switzerland Hydropower Change in runoff and timing Oberhasli, Switzerland Hydropower change in timing of runoff Göschener alp reservoir, Switzerland Hydropower change in timing of input Gougra, Switzerland Hydropower increase in input Gougra, Switzerland Hydropower change in timing of input Snow cover - Slightly more precipitation/snow, slightly less snow cover, slight increase in snow melt Glaciers - significant reduction, decrease of glacier melt with slightly earlier maximum Snow cover - minor change of seasonality Glaciers - significant reduction, increase in runoff Snow cover - change in timing of runoff Prättigau, Switzerland Hydropower slight increase in runoff Glaciers - slight decline Do Not Cite, Quote or Distribute SM2-41 Slight glacier decline Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Location Affected Sector or System Impact Prättigau, Switzerland Hydropower change in runoff and timing Switzerland Hydropower Italian Alps Hydropower Increased water inflow Decreased water supply for run-ofriver hydropower Slightly more precipitation/snow, slightly less snow cover, slight increase in snow melt and winter discharge Glacier retreat Glacier retreat has reduced summer runoff. Increase in rock avalanche frequency Glacier retreat and permafrost degradation M neg Permafrost degradation M neg Permafrost thaw H neg Ravanel and Deline (2011); Fischer et al. (2012); Ravanel et al. (2017) Stoffel and Graf (2015) Roer et al. (2008) Permafrost thaw H neg Kummert et al. (2017) Permafrost thaw H neg Bodin et al. (2016) Permafrost thaw H neg Ravanel et al. (2017) Permafrost thaw H neg Ravanel et al. (2013) Permafrost thaw H neg Permafrost thaw M neg Ravanel et al. (2010) Ravanel and Deline (2011) Permafrost degradation M neg Changes in snow cover characteristics M neg Changes in snow cover characteristics M pos Changes in snow cover characteristics M pos Gadek et al. (2017) Change in duration and depth of snow cover and change in precipitation type (rain vs. snow) M pos Freudiger et al. (2014); Moran-Tejéda et al. (2016) French and Italian Alps Landslides Swiss Alps Landslides European Alps Landslides European Alps Landslides European Alps Landslides European Alps Landslides European Alps Landslides European Alps Landslides European Alps Landslides Swiss Alps Landslides European Alps European Alps Tatras mountains European Alps Snow avalanche Snow avalanche Snow avalanche Floods Do Not Cite, Quote or Distribute Cryosphere Change Increase in frequency of large debris flows Rock glacier destabilisation Increasing debris flows and small rock fall Rock glacier collapse Increasing rockfall during heat waves Slope instability beneath infrastructure Increasing rockfall Increasing rockfall during recent decades Increase in debris transport into steep slopes and destabilisation of rock glaciers More avalanches involving wet snow Decrease in total number of avalanches at lower elevation Decline in mass and intensity of large avalanches Decrease in rain-on snow flood event at lower elevation and in spring SM2-42 Total pages: 87 Attribution Confidence Positive/Ne gative/Mix ed Reference H mixed “ H pos Schaefli et al. (2019) M neg Orlove et al. (2019) Kääb et al. (2007) Pielmeier et al. (2013) Naaim et al. (2016) Eckert et al. (2013); Lavigne et al. (2015) FINAL DRAFT Chapter 2 Supplementary Material Location Affected Sector or System European Alps Floods Poland (Białowieża Forest) Terrestrial ecosystems Pyrenees Swiss Alps Italian Alps French Pyrenees French Pyrenees French Pyrenees Swiss Alps Italian Alps Western Balkans Austrian Alps Austrian Alps Italian Alps Terrestrial ecosystems Terrestrial ecosystems (tundra) Terrestrial ecosystems (tundra) Freshwater ecosystems Freshwater ecosystems Freshwater ecosystems Freshwater ecosystems Freshwater ecosystems Freshwater ecosystems Freshwater ecosystems Freshwater ecosystems Freshwater ecosystems IPCC SR Ocean and Cryosphere Impact Cryosphere Change Attribution Confidence Positive/Ne gative/Mix ed Reference Increase in rain-on snow flood event at higher elevation and in winter increased predation pressure in a mammal (weasel) due to phenological camouflage mismatch availability duration of high quality food for a bird (ptarmigan) Alpine grassland species colonize the snowbeds Change in duration and depth of snow cover and change in precipitation type (rain vs. snow) M neg “ decreasing number of snow-cover days M neg Atmeh et al. (2018) Earlier snow-melt M pos García-González et al. (2016) Shorter snow-cover duration H mixed Matteodo et al. (2016) Glacier retreat H mixed D'Amico et al. (2017) Decreased runoff due to glacier decline M neg Khamis et al. (2015) Decreased runoff due to glacier decline H pos/neg Khamis et al. (2016) Reduction in genetic diversity Decreased runoff due to glacier decline M neg Finn et al. (2013) Upward shift of invertebrate taxa Decreased runoff due to glacier decline H neg Finn et al. (2010) Loss of endemic invertebrates Decreased runoff due to glacier decline H neg Finn et al. (2013) Loss of native trout Decreased runoff due to glacier decline M neg Papadaki et al. (2016) Increased diatom biodiversity Decreased runoff due to glacier decline M pos Fell et al. (2018) Increased microbial biodiversity Decreased runoff due to glacier decline M pos Finn et al. (2009) Range reduction in trout Decreased runoff due to glacier decline M neg Vigano et al. (2016) Slow soil and plant community development Change in species interactions and loss of taxa Increased local diversity; decreased regional diversity European Alps Infrastructure Structure instability Permafrost thaw M neg Phillips and Margreth (2008) European Alps and Pyrenees Tourism Reduction in ski lift revenues and operating capabilities of ski resorts Reduction of snow cover duration H neg Steiger et al. (2017) Do Not Cite, Quote or Distribute SM2-43 Total pages: 87 FINAL DRAFT Location Chapter 2 Supplementary Material Affected Sector or System European Alps Tourism Italian Alps Culture Italian Alps Culture IPCC SR Ocean and Cryosphere Impact Cryosphere Change Changes in the safety of mountaineering routes Glacier decline, permafrost thaw (impact on ground instability) H neg Ritter et al. (2012); Duvillard et al. (2015); Ravanel et al. (2017); Mourey et al. (2019) Glacier retreat H neg Brugger et al. (2013) Reduced ice and snow cover H neg Jurt et al. (2015) Aesthetic quality; Local residents find the dark peaks in summer to be unattractive Local residents feel that the identity of their village is weakening as the peaks have less ice and snow Attribution Confidence Positive/Ne gative/Mix ed Reference Scandinavia/Nordic Northern Norway Hydropower More water for hydropower Thinning of glacier, changed routing of glacier-dammed lake H pos Engeset et al. (2005) Northern Norway Landslides Increase in debris transport into steep slopes Increase in rock glacier speed M neg Eriksen et al. (2018) abundance reduction of a small mammal (mountain hare) due to molting mismatch and predation snow cover duration M neg Pedersen et al. (2017) glacier retreat H pos Matthews and Vater (2015) Reduced snow cover duration M neg Falk and Vieru (2017) Terrestrial ecosystems Norway (tundra; forest) Terrestrial Norway ecosystems (tundra) Finland Tourism Caucasus and Middle East invertebrate, plant and fungal community composition change during succession Reduction in ski lift revenues Central Caucasus Snow avalanche Increased risk of large avalanches Glacier decline, change in snow conditions M neg Central Caucasus Floods Increased risk of outburst floods Glacier decline, permafrost thaw (impact on ground instability) M neg Western Caucasus North Asia Tourism Ski tourism Reduction of snow cover duration M neg Terrestrial ecosystems (tundra) Plant and fungal community composition change during succession Glacier retreat H mixed Russia (Altai mountains) Southern Andes Do Not Cite, Quote or Distribute SM2-44 Total pages: 87 Aleynikov et al. (2011) Volodicheva et al. (2014) Petrakov et al. (2012) Chernomorets et al. (2018) Sokratov et al. (2014) Cazzolla Gatti et al. (2018) FINAL DRAFT Location Central Chile Chapter 2 Supplementary Material Affected Sector or System Water resources IPCC SR Ocean and Cryosphere Impact Cryosphere Change Attribution Confidence Positive/Ne gative/Mix ed Reference Reduced water supply reserves Reduction and melt/collapse of rocky glaciers Low/M neg Navarro et al. (2018) Glacier decline H neg Navarro et al. (2018); Wilson et al. (2018) Colavitto et al. (2012) M neg Pizarro et al. (2013) Low/M neg Landaeta et al. (2012) Patagonia Floods Increase in size and number of glacier lakes; risk of outburst floods (e.g. at new locations) Central Chile Floods Peak floods (no specific affected sectors mentioned) Chilean Patagonia Freshwater ecosystem Spawn rates for certain fish species negatively affected (some of great commercial value for the region) Low Latitudes Cordillera Blanca, Peruvian Andes Water resources Drinking water supply in rural areas Reduced glacier contribution to groundwater which maintains springs H neg Baraer et al. (2012) Peruvian Andes Agriculture Negative impact on crops, pastures and livestock Reduced runoff due to glacier retreat M neg Mark et al. (2010); Bury et al. (2011) Constrained plant primary succession Glacier retreat M neg (Zimmer et al., 2018) upward shifts of vegetation zones and maximum elevation of species Glacier retreat H pos Morueta-Holme et al. (2015) Decrease in regional biodiversity Reduced runoff due to glacier decline M neg Milner et al. (2017) Loss of regional diversity Reduced runoff due to glacier decline H neg Cauvy-Fraunié et al. (2016) Downstream shift of macroinvertebrates Reduced runoff due to glacier decline M pos Jacobsen et al. (2014) Tourism Closure of a ski resort. Glacier disappearance, reduced snow cover H neg Kaenzig et al. (2016) Culture Spiritual value: concern among local residents who seek to restore relations with the local mountain deity. Glacier retreat and lesser snowmelt on a major mountain have reduced flow in a river H neg Stensrud (2016) Central Andes (Bolivia, Peru) Northern Andes (Ecuador) Ecuador Ecuador Ecuador Tropical Andes Peruvian Andes Terrestrial ecosystems (tundra) Terrestrial ecosystems (tundra) Freshwater ecosystems Freshwater ecosystems Freshwater ecosystems Do Not Cite, Quote or Distribute SM2-45 Snow and glacier melt, shifts in peak flow (currently increasing), affecting water security in dry months Changes in water temperature and salinity due to changes ice and snow melt Total pages: 87 FINAL DRAFT Location Chapter 2 Supplementary Material Affected Sector or System Ecuadorian Andes Culture Peruvian Andes Culture Peruvian Andes Migration Bolivian Andes Migration Impact Loss of Indigenous knowledge, especially among youth and children, in a setting where such knowledge is closely linked to the physical presence of the glacier Spiritual value: the site of a major pilgrimage was altered, making it more difficult for pilgrims to access the site, and creating distress and concern for them Emigration and increased wage labour migration: Glacier runoff used to irrigate pasture, so herders increased their temporary migration for wage labour opportunities; the greater propensity of younger adults to migrate alters the demographic composition of the herding community, with a larger proportion of elderly and female than previously. Increased emigration and declines in the productivity of irrigated agriculture IPCC SR Ocean and Cryosphere Cryosphere Change Attribution Confidence Positive/Ne gative/Mix ed Reference Glacier decline and disappearance M neg Rhoades et al. (2008) Glacier retreat H neg Allison (2015) Reduced runoff due to glacier retreat and lesser snowmelt runoff M neg Alata et al. (2018) Reduced runoff due to glacier retreat M neg Brandt et al. (2016) Glacier retreat and reduced snow cover M neg McDowell et al. (2013) Increased/ decreased runoff due to glacier decline and change in snowpack H mixed Lutz et al. (2016b) Reduced runoff due to glacier retreat and less snowmelt H neg Nüsser and Schmidt (2017) Reduced snow cover duration M neg Shaoliang et al. (2012) More erratic snowfall M neg Gentle and Maraseni (2012) High Mountain Asia Nepal Water resources Several regions Hydropower Gilgit-Baltistan, Pakistan Agriculture Nepal Agriculture Nepal Agriculture Do Not Cite, Quote or Distribute Drinking water supply in rural areas reduced More/less water for hydropower depending on timing for different regions. Reduced water availability for irrigation of crops on a major mountain Reduction in quality of pasture, which reduces the capacity of the area to support livestock Decreased agricultural production SM2-46 Total pages: 87 FINAL DRAFT Chapter 2 Supplementary Material Location Affected Sector or System Nepal Agriculture Nepal Agriculture Pakistan Agriculture Nepal Agriculture Himalaya Snow avalanche Himalaya Floods Himalaya Floods Himalaya Floods Himalaya Floods China (Tibetan plateau, Hailuogou glacier) Terrestrial ecosystems (forest) Terrestrial ecosystems (tundra) Terrestrial ecosystems (tundra) Quinghai-Tibetan Plateau Himalayas (Ladakh) Tibetan Plateau Terrestrial ecosystems (tundra) Bhutan Terrestrial ecosystems (tundra) Do Not Cite, Quote or Distribute Impact Less favourable potato planting conditions Reduced soil moisture, which reduces crop yield Irrigation Reduced yields due drying of soils in winter and reduced moisture input in spring Increase in occurrence of avalanches Increase in size and number of glacier lakes Risk of outburst floods (e.g. at new locations) Increased exposure of (growing) tourism/pilgrims to glacier lake outburst floods Increase in exposure of hydropower plants to glacier lake outburst floods fungal community composition change during succession Plant species’ upslope and northward range shift; range expansion Upslope range shift above the limit of continuous plant distribution; decrease in plant cover Reduction of plant productivity (above ground net primary productivity); plant species diversity loss Plant establishment as snowline shifts upward; greater plant productivity SM2-47 IPCC SR Ocean and Cryosphere Cryosphere Change Attribution Confidence Positive/Ne gative/Mix ed Reference Seasonally delayed snowfall M neg Sujakhu et al. (2016) Reduced snow cover M neg Prasain (2018) Reduced runoff due to glacier retreat M neg Nüsser and Schmidt (2017) Reduced snow cover M neg Smadja et al. (2015) Change in snow conditions (more wetsnow conditions) M neg Glacier retreat H mixed Glacier retreat led to increase in number and size of glacier lakes H neg Glacier retreat and lake formation H neg Uniyal (2013) Glacier retreat and lake formation M neg Schwanghart et al. (2016) Glacier retreat H pos Tian et al. (2017) Permafrost reduction H pos You et al. (2018) Extreme snowfall year H mixed Dolezal et al. (2016) M neg Yang et al. (2018) M mixed Wangchuk and Wangdi (2018) Permafrost thaw Ascent of snowline Total pages: 87 Ballesteros-Cánovas et al. (2018) Frey et al. (2010); (Gardelle et al., 2011) Carrivick and Tweed (2016); Harrison et al. (2018); Veh et al. (2019) FINAL DRAFT Location Northern China, Northwest China, Tibetan Plateau Tibetan Plateau Chapter 2 Supplementary Material Affected Sector or System Terrestrial ecosystems (forest) Terrestrial ecosystems (tundra) Himalaya and Tibetan Plateau Tourism Bhutan Tourism Tibet Culture Tibetan Plateau Culture Uttarakhand, India Culture Nepal Culture Nepal Culture Nepal Migration Impact Greater tree growth in regions with more snow; no effect of snow where snow accumulation is low greenness change for alpine meadow and alpine steppe across much of the Plateau Changes in access routes to Baishui Glacier No. 1 High elevation trekking: trails damaged and trekking routes limited Spiritual value: a number of sacred mountains are altered, causing distress for the local population, who view this change as the product of their own spiritual and moral failings Aesthetic value of glaciers reduced Spiritual value - rising concern for local population who view the changes in sacred mountains as the product of their own religious and moral failings Identity and aesthetic values (threatened as beauty of mountains is reduced) Causing people to experience concern about divine beings and proper rituals Increased emigration due to declining irrigation water and agricultural yields IPCC SR Ocean and Cryosphere Cryosphere Change Attribution Confidence Positive/Ne gative/Mix ed Reference Snow accumulation H mixed Wu et al. (2018) Permafrost presence or absence; soil moisture H mixed Wang et al. (2016) Glacier retreat M neg Wang et al. (2010) Increased runoff due to increased snowmelt and glacier melt M neg Hoy et al. (2016) Glacier retreat M neg Salick et al. (2012) Glacier surfaces have become dirtier M neg Wang et al. (2017a) Glacier retreat M neg Drew (2012) Glacier retreat and reduction in snow cover M neg Konchar et al. (2015) Reduced snow cover M neg Becken et al. (2013) Reduced runoff due to less snow cover M neg Prasain (2018) New Zealand New Zealand Landslides Rock avalanches from lower permafrost limit Thaw/degradation of permafrost M neg Allen et al. (2011) New Zealand Freshwater ecosystems Loss of cold tolerant taxa Reduced runoff due to glacier decline M neg Cadbury et al. (2010) Do Not Cite, Quote or Distribute SM2-48 Total pages: 87 FINAL DRAFT Location Chapter 2 Supplementary Material Affected Sector or System IPCC SR Ocean and Cryosphere Impact Cryosphere Change Attribution Confidence Positive/Ne gative/Mix ed Reference Changes in vegetation structure (shrubs & forbs) Accelerated snow melt and drier soil conditions M mixed Amagai et al. (2018) Plant (bamboo) encroachment into alpine zones Changes in water balance associated with snowmelt M pos Winkler et al. (2016) Closure of ski resorts Reduced snow fall and snow cover H neg Beaudin and Huang (2014); Hamilton et al. (2003) Other regions Japan (Taisetsu Mountains, Hokkaido) Japan (Taisetsu Mountains, Hokkaido) New England, North East USA Terrestrial ecosystems (tundra) Terrestrial ecosystems (forest) Tourism Do Not Cite, Quote or Distribute SM2-49 Total pages: 87 FINAL DRAFT SM2.9 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Details of Studies on Adaptations in Response to Cryosphere Changes Table SM2.12: Documented individual adaptation actions, per country (grouped by regions as defined in Figure 2.1), for sectors addressed in this chapter, i.e. Agriculture, Biodiversity, Water, Energy, Natural Hazards (Hazards), Tourism & recreation (Tourism), Settlements & habitability (Habitability), Intrinsic & cultural values (Cultural). ‘Other’ is a merged category for other sectors and ‘Undefined’ refers to adaptation where no clear classification to a specific sector could be allocated. The adaptations are listed across their scale of relevance and/or implementation (Local, Regional, Global), as well as classification of type of adaptation as either ‘formal policy’, ‘autonomous’ or ‘undefined’. Key climatic drivers are listed that have links to (or changes in) cryosphere changes are described, which include: Temperature change ‘Temperature’; Precipitation change in terms of amount and timing (‘Precip. (amount, timing)’); Precipitation change in terms of changes in state (e.g. snow to rain) (‘Precip. (phase)’); Glacier change where non-hydrological impacts were associated (‘Glacier (non-hydro)’); Glacial hydrology change (‘Glacier (hydro)’); Snow cover change where non-hydrological impacts were associated (‘Snow (nonhydro)’); Snow hydrology change (‘Snow (hydro)’); Extreme events where hydrological elements were associated (‘Extremes (hydro)’); Extreme events that were not associated with a hydrological impacts (‘Extremes (non-hydro)’); ‘Permafrost thaw’; and ecosystem changes in terms of flora and/or fauna (‘Ecosystem’). Entries for each regions are sorted in alphabetical order of the references. Scale of Region Type of Sector Description of Adaptation Climatic Driver of Adaptation Reference relevance / adaptation Country implementation Alaska USA Undefined Multi-stakeholder adaptation planning exercise Regional Undefined Snow (non-hydro), Ecosystem Knapp et al. (2014) Instillation of GLOF early warning system Regional Formal Policy Glacier (hydro), Extremes (hydro) Petrakov et al. (2012) Formal Policy Temperature, Precip. (amount, timing), Glacier (hydro) Beniston et al. (2011) Global Undefined Temperature, Precip. (amount, timing, phase state), Glacier (hydro), Extremes (hydro, nonhydro), Permafrost thaw Beniston and Stoffel (2014) Regional Autonomous Temperature, Precip. (amount, timing), Snow (non-hydro) Campos Rodrigues et al. (2018) Caucasus and Middle East Russia Hazards Central Europe Water Switzerland Water, Hazards Efforts of ACQWA projects to address vulnerability associated with hydrological changes Flooding/hazards planning - Third Rhone Correction Regional Local, Regional Flooding/hazards planning - MINERVE Switzerland, Agriculture, Italy, Chile, Energy, Water Kyrgyzstan Impact assessment for adaptation planning Artificial snow production Spain Tourism Nocturnal skiing Protection and conservation of snowpack Diversification of snow-based activities Do Not Cite, Quote or Distribute SM2-50 Total pages: 87 FINAL DRAFT Region Country Sector Chapter 2 Supplementary Material Description of Adaptation IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Local Autonomous Temperature, Glacier (nonhydro, hydro), Permafrost thaw Duvillard et al. (2015) Local Autonomous Snow (non-hydro) Fischer et al. (2011) Regional Autonomous Temperature, Precip. (amount, timing), Snow (non-hydro) Grünewald et al. (2018) Glacier (hydro), Snow (hydro), Extremes (hydro), Permafrost thaw Haeberli et al. (2016) Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro) Hill (2013) Hill et al. (2010) Expansion of skiable area Accessing economic assistance (gov & insurance) Turning ski resorts into multi-recreation facility France Tourism, Hazards Austria Tourism Switzerland Italy Tourism Tourism Hazards Switzerland Undefined Water Switzerland Water Installation of ladders Cover ski runs with textile to reduce ablation Grooming ski slopes Cover snow with sawdust to preserve for skiing Installing a hanging bridge across the deep gorge to allow mountain access Local Installation of early warning system Project to support adaptation planning - NELAK Lake level lowering Flood retention Autonomous Undefined Regional Formal Policy Undefined Undefined Policy incentives for ‘‘resilience- based’’ water infrastructure projects Shared water utility service to spread risks among Regional stakeholders Policy for reducing water use in periods of drought Formal Policy Undefined Artificial snow production Switzerland Tourism Undefined Switzerland, Energy, Water France Tourism Do Not Cite, Quote or Distribute Consortium for tourism planning and diversification Project to support adaptation planning - CIPRA Glacier-fed rivers and climate change project GLAC-HYDROECO-NET Establishment of Chamonix Department of Trail Maintenance SM2-51 Undefined Autonomous Regional Formal Policy Temperature, Glacier (nonhydro, hydro), Snow (nonhydro), Permafrost thaw, Ecosystem Undefined Formal Policy Glacier (hydro), Ecosystem Khamis et al. (2014) Local Formal Policy Temperature, Glacier (nonhydro, hydro), Permafrost thaw Mourey and Ravanel (2017) Total pages: 87 FINAL DRAFT Region Country France Sector Description of Adaptation Tourism, Hazards Construction of bridge to access to refuge on Mont Blanc Route modifications, opening trail connecting other refuges Installation of ladders Austria, Germany, Undefined Switzerland Austria Austria, Tourism Switzerland Italy Switzerland Hazards Spain Tourism Tourism Spain Chapter 2 Supplementary Material Undefined Austria Tourism Austria Tourism Assessment of adaptation knowledge and needs IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Autonomous Global Formal Policy Glacier (hydro), Snow (hydro), Extremes (hydro) Undefined Glacier (non-hydro), Snow (nonhydro) Muccione et al. (2016) Switching to other tourism activities Resorts covering glaciers Redistributing available snow Undefined Creating hazard maps and restricting construction Modelling how ski area change and tourism impacts in support of planning process Artificial snow production Undefined Formal Policy Glacier (hydro), Snow (nonhydro), Extremes (hydro) Formal Policy Temperature, Snow (non-hydro) Pons-Pons et al. (2012) Autonomous Project to support adaptation planning - ESPON- Undefined CLIMATE Evaluation of impacts of climate change on alpine Regional trails to support planning Artificial snow production Orlove (2009b) Regional Formal Policy Snow (non-hydro) Pons et al. (2014) Formal Policy Glacier (hydro), Permafrost thaw Ritter et al. (2012) Autonomous Temperature, Snow (non-hydro) Formal Policy Precip. (amount, timing), Glacier Azhoni and Goyal (hydro), Extremes (hydro) (2018) Steiger and Mayer (2008) High Mountain Asia India Development of state action plan on climate change Agriculture Hazard risk and vulnerability assessment to support planning Agriculture, Water Spring water rejuvenation project Habitability India Other Undefined Do Not Cite, Quote or Distribute Regional Local Building stone embankments to avoid flooding Increase the range of crops covered under insurance Improving access to better technology in agriculture SM2-52 Local Undefined Temperature, Precip. (amount, timing), Extremes (hydro) Temperature, Precip. (amount, timing) Total pages: 87 Bhadwal et al. (2013) FINAL DRAFT Region Country Chapter 2 Supplementary Material Sector Description of Adaptation Agriculture Capacity building for farmers for water efficient farm practice IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Temperature, Precip. (amount, timing), Extremes (hydro) Limiting cultivation of summer rice Agriculture, Water Field bunding to control erosion Afforestation Temperature, Precip. (amount, timing) Promoting water efficient irrigation Construction of water harvesting and storage structure Water Climatic Driver of Adaptation Reference Increase public awareness of water conservation Knowledge sharing exercises Water conservation structure like dams, surface water bodies, field bunding Temperature, Precip. (amount, timing), Extremes (hydro) Water harvesting structures Tajikistan Agriculture, Energy, Culture, Stakeholder workshop providing information for Habitability, Water, adaptation planning Other Undefined National Adaptation Programme of Action Nepal Formal Policy Temperature, Precip. (amount, timing), Glacier (non-hydro) Bizikova et al. (2015) Snow (non-hydro), Extremes (hydro) Byers et al. (2014) Formal Policy Local Adaptation Plan of Action Research and monitoring of glacial lakes Early warning systems Nepal Undefined Disaster management systems Weather monitoring and forecasting Snow and ice management training Regional Undefined Alternative house construction strategies Public awareness building Firefighting training and equipment Do Not Cite, Quote or Distribute SM2-53 Total pages: 87 FINAL DRAFT Region Country Chapter 2 Supplementary Material Sector Description of Adaptation Other Insurance coverage and clothing for porters Agriculture Nurseries and afforestation IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Labour migration Undefined Appointed villager to regularly check all glaciers Opening a training center for adaptation in mountain villages Planting trees Tajikistan Autonomous Initiate a watershed development committee Glacier (hydro), Ecosystem Building water reservoir Crop and livestock diversification Agriculture Undefined Uzbekistan Agriculture Christmann and AwHassan (2015) Local Supporting education of local person in agriculture and engineering to increase adaptation capacity in community Participatory discussion of adaptation strategies for rangeland Establish pastoral user groups Establish fenced seed isles for yearly natural seeding Formal Policy Temperature, Precip. (amount, timing), Glacier (hydro) Autonomous Temperature, Glacier (hydro) Clouse (2014) Autonomous Snow (hydro) Banerji and Basu (2010) Autonomous Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro) Clouse (2016) Seasonal grazing management India Water India Water India Undefined Artificial glacier construction Local Reservoirs built and snow fences installed to capture/store snow in winter for use as irrigation Local in summer Moving to new location to escape perennial water scarcity Reduce overall hectare of cropland in production Local Shrink livestock holding to fit available pasturage Habitability Do Not Cite, Quote or Distribute Snow barrier bands SM2-54 Total pages: 87 FINAL DRAFT Region Country India Chapter 2 Supplementary Material Sector Description of Adaptation Habitability, Water Building new irrigation canals and rerouting water Culture Use of reservoirs to store water Water Evaluation of artificial ice reservoirs Agriculture Installation of improved water mills IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Formal Policy Regional Autonomous Temperature, Glacier (hydro) Clouse et al. (2017) Agriculture, Water Building ice stupa to store water Local India Agriculture Government watershed improvement programs Regional Formal Policy Glacier (hydro), Snow (hydro) Dame and Nüsser (2011) India Undefined Spread coal onto glaciers to ensure regeneration Local Autonomous Temperature, Precip. (amount, timing), Glacier (hydro) Gagné (2016) India, Nepal, Pakistan Undefined Collaborative adaptation research initiative CARIAA Regional Formal Policy Glacier (hydro), Snow (hydro) Cochrane et al. (2017) Nepal Water Local Autonomous Precip. (amount, timing), Extremes (hydro, non-hydro) Becken et al. (2013) Agriculture Multiple livelihood options to buffer against seasonal losses in one sector Switching crop types Early warning systems and community-based flood management Training for flood preparedness and responses Undefined Using traditional remedies to rehabilitate victims of diseases Borrowing from neighbours Autonomous Local Vulnerable Group Feeding program Framework and strategy for disaster risk management National strategy for disaster risk management Nepal Glacier (hydro), Snow (hydro) Precip. (amount, timing), Glacier Dewan (2015) (hydro), Extremes (non-hydro) Formal Policy Flood risk reduction program Water Hazards Do Not Cite, Quote or Distribute Building tube wells for drinking water Raising houses on stilts Funds to support social resilience SM2-55 Undefined Undefined Total pages: 87 FINAL DRAFT Region Country China Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Sector Description of Adaptation Scale of Type of relevance / adaptation implementation Undefined Policies to address the impact of permafrost degradation Undefined Special fund for climate change adaptation Regional Climatic Driver of Adaptation Reference Formal Policy Permafrost thaw Fang et al. (2011) China Undefined Project to support adaptation planning - RECAST Regional Formal Policy Precip. (amount, timing), Glacier Fricke et al. (2009) (hydro) China Habitability Relocation of settlement Autonomous Extremes (hydro) Diemberger et al. (2015) Temperature, Glacier (nonhydro) Wang et al. (2010) Temperature, Precip. (amount, timing), Snow (non-hydro) Fu et al. (2012) Undefined Temperature, Precip. (amount, timing), Glacier (hydro) Gao et al. (2014) Formal Policy Glacier (hydro), Extremes (hydro) Kattelmann (2003) Autonomous Temperature, Precip. (amount, timing), Extremes (hydro), Ecosystem Gentle and Maraseni (2012) Local Assessment to support sustainable glacier tourism China Tourism Tourism diversification Formal Policy Regional Restricting tourism access Shifting to different seasonal pasture Sharing pasture within community China Agriculture Cultivating fodder to feed in winter Build small livestock sheds Local Autonomous Selling new products Pasture management activities Agriculture, Water Water saving irrigation measures China Nepal Agriculture Rotational grazing Undefined Fencing grassland and grass planting Hazards GLOF early warning system Formal Policy Regional Creating community forest user groups Reliance on traditional institutional arrangements Storage of grains Nepal Agriculture Local Purchasing irrigated land Switch to new agriculture technology/crop types Institutional support from Community Forest User Groups Do Not Cite, Quote or Distribute SM2-56 Total pages: 87 FINAL DRAFT Region Country Chapter 2 Supplementary Material Sector Description of Adaptation Agriculture, Culture, Water Transhumant pastoralism as adaptation strategy IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Money lending Cash saving Undefined Take loans in times of food scarcity Reduce food intake Migration/selling labor Agriculture, Kyrgyzstan Energy, Water Kyrgyzstan Agriculture Kyrgyzstan, Water Uzbekistan Impact assessment for adaptation planning Introduction of new crops with lower water requirements Establishment of centre for transboundary water governance Temperature, Precip. (amount, timing, phase state), Glacier (hydro), Extremes (hydro, nonhydro), Permafrost thaw Temperature, Glacier (hydro), Snow (hydro) Beniston and Stoffel (2014) Global Undefined Local Autonomous Regional Formal Policy Glacier (hydro) Hoelzle et al. (2017) Local Autonomous Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro), Ecosystem Ingty (2017) Regional Formal Policy Local Formal Policy Glacier (hydro) Nüsser et al. (2018) Temperature, Precip. (amount, timing), Glacier (hydro), Extremes (hydro) Kaul and Thornton (2014) Hill et al. (2017) Growing crops at higher altitudes Agriculture Regulate agriculture and grazing rights to allow ecosystem recovery Storage and crop fodder India Agriculture, Culture Reliance on traditional knowledge Diversify to tourism Tourism Migration State action plan on climate change India India Habitability, Water Evaluating efficacy of artificial glaciers Hazards DRR demonstration in schools Agriculture Populating potato and peas Agriculture, Other Insurance schemes for crops Do Not Cite, Quote or Distribute SM2-57 Local Undefined Formal Policy Undefined Formal Policy Total pages: 87 FINAL DRAFT Region Country Chapter 2 Supplementary Material Sector Description of Adaptation Water Participatory project to underpin adaptation planning Agriculture India IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Local Formal Policy Precip. (amount, timing), Glacier Kelkar et al. (2008) (hydro), Snow (hydro) Local Autonomous Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro), Extremes (hydro) Plant less water-intensive crops Irrigate fields timeshare Sell land and livestock Undefined Find other jobs Take loans Agriculture Nepal Diversify to tourism, agropastoralism, agroforestry Undefined New roofing material Agriculture Nepal Tourism Nepal Habitability Nepal Nepal Construction of greenhouses Agriculture, Tourism Nepal Nepal Crop diversification changing crops and agricultural practices using Local Indigenous and local knowledge Assessment of ecotourism as adaptation measure Regional for conservation area Local relocation of settlement after decreased Local water supply Autonomous Undefined Nepal Temperature, Snow (non-hydro), Manandhar et al. (2011) Snow (hydro) Precip. (amount, timing, phase Adler et al. (2013) state), Extremes (non-hydro) Autonomous Snow (hydro) Barnett et al. (2005) Local Autonomous Temperature, Precip. (amount, timing), Snow (non-hydro) Onta and Resurreccion (2011) Agriculture Crop diversification Undefined Cross-border trade and day-labour trips Water Lake lowering Regional Formal Policy Extremes (hydro) Orlove (2009b) Undefined Project to support adaptation planning - Climate Witness Project Regional Formal Policy Glacier (hydro), Snow (nonhydro), Extremes (hydro) Rai and Gurung (2005) Undefined Formal Policy Glacier (hydro), Extremes (hydro) Somos-Valenzuela et al. (2015) Local Autonomous Temperature, Precip. (amount, timing), Glacier (hydro), Extremes (hydro) McDowell et al. (2013) Establishing a Designated National Authority Nepal Konchar et al. (2015) Undefined Water Do Not Cite, Quote or Distribute Lake lowering Modelling impact of GLOF to support planning Limiting water consumption to drinking and cooking requirements Roof water collection system SM2-58 Total pages: 87 FINAL DRAFT Region Country Sector Chapter 2 Supplementary Material Description of Adaptation IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Regional Formal Policy Glacier (hydro), Snow (hydro), Extremes (hydro) Lebel et al. (2010) Local Autonomous Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro) Meena et al. (2019) Local Autonomous Precip. (amount, timing), Glacier Maikhuri et al. (2017) (hydro), Extremes (hydro) Regional Formal Policy Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro), Extremes (hydro) Meenawat and Sovacool (2011) Global Formal Policy Glacier (hydro), Snow (hydro), Extremes (hydro) Muccione et al. (2016) Formal Policy Temperature, Precip. (amount, timing), Glacier (hydro), Extremes (hydro) Moors et al. (2011) Autonomous Temperature, Precip. (amount, timing), Glacier (hydro), Ecosystem Negi et al. (2017) Hire assistants to help with water retrieval activities Undefined Nepal, India Hazards, Water Collecting fuelwood for heating Bilateral Committee on Flood Forecasting Crop diversification India Agriculture Change timing of agricultural activities Agropastoralism to diversify livelihood Changing agricultural patterns Switching to other types of animal husbandry India Agriculture Adopt horticulture Establish forest councils and village forest committee Migration Undefined Take loans and insurance Hazards Instillation of GLOF early warning system Lowering lake water levels Bhutan Undefined Community awareness and capacity building activities GLOF Risk Reduction Projects Bhutan, Nepal Undefined Assessment of adaptation knowledge and needs India National Action Plan on Climate Change India Water National Water Policy Undefined Project to support adaptation planning - Highnoon Regional India Agriculture Do Not Cite, Quote or Distribute Crop diversification Local Crop diversification SM2-59 Total pages: 87 FINAL DRAFT Region Country Sector Chapter 2 Supplementary Material Description of Adaptation IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Agropastoralism to diversify livelihood Convert irrigated land into rainfed Switching away from livestock rearing Use of moisture conserving cropping techniques Undefined Migration Extremes (hydro) Pakistan Habitability Relocation after hazard event Local Autonomous Extremes (hydro, non-hydro) Kreutzmann (2012) Pakistan Water Construction of water channels for irrigation and domestic water supply Local Autonomous Glacier (hydro) Nüsser and Schmidt (2017) Pakistan Undefined Migration Local Autonomous Glacier (hydro), Snow (hydro) Parveen et al. (2015) Pakistan Undefined Local Autonomous Precip. (amount, timing), Glacier (hydro), Extremes (hydro, non- Shah et al. (2017) hydro) Local Autonomous Temperature, Precip. (amount, timing), Glacier (hydro) Spies (2016) Formal Policy Temperature, Glacier (hydro), Snow (hydro) Sorg et al. (2014b) Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro) Stucker et al. (2012) Household renovations Precautionary savings Irrigation scheme/program Pakistan Water Kyrgyzstan, Tajikistan, Undefined Uzbekistan, Kazakhstan Poverty alleviation and physical infrastructure development program Identification of steps for overcoming adaptation Regional challenges - ACQWA project Water user associations Water allocation strategy Water rationing Kyrgyzstan, Water Tajikistan Do Not Cite, Quote or Distribute Formal Policy Water sharing Integrate IWRM principles into institutions Clean and repair canals Agriculture Regional Undefined Local Autonomous Expand orchards SM2-60 Total pages: 87 FINAL DRAFT Region Country Sector Chapter 2 Supplementary Material Description of Adaptation IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Do not plant a second crop Crop diversification Hazards Early warning system Undefined Integrated Water Resource Management project Agriculture, Biodiversity, Development of sectoral adaptation plans Energy, Hazards, Water Agriculture, Kazakhstan Habitability, Water Introduction of water-saving technologies Undefined Formal Policy Regional Decrease livestock pressure on pasture Agriculture Formal Policy Realization of pasture management plans Establishment of the Public Seed Funds Tajikistan Water Agriculture, Biodiversity, Water Agriculture, Hazards, Water Development of water user associations Environmental land management and rural livelihoods project Capacity strengthening and livelihood diversification project Habitability Infrastructure improvements Glacier (hydro), Snow (hydro), Extremes (hydro) Local Developing evacuation maps Hazards Autonomous Constructing shelters for hazard protection Training of volunteers for the search and rescue activities Agriculture, Initiation of Ecosystem-based Adaptation (EbA) Biodiversity, Water Kazakhstan, Agriculture, Kyrgyzstan, Knowledge sharing arrangements Hazards, Water Tajikistan Documentation, dissemination, and preservation Agriculture, Water of local knowledge relevant to adaptation Regional Formal Policy Local Low Latitudes (Andes) Do Not Cite, Quote or Distribute SM2-61 Total pages: 87 Xenarios et al. (2018) FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Region Country Sector Description of Adaptation Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Bolivia Undefined Migration Local Autonomous Glacier (hydro) Bolivia Water Construction of reservoirs for water storage Regional Formal Policy Bolivia Undefined Migration Local Autonomous Bolivia Tourism Rebranding the loss of glaciers as an opportunity for "last chance tourism" Regional Autonomous Brandt et al. (2016) Temperature, Precip (amount, Buytaert et al. (2017) timing), Glacier (hydro) Temperature, Glacier (hydro), Kaenzig (2015) Snow (hydro), Extremes (hydro) Temperature, Precip. (amount, Kaenzig et al. (2016) timing), Snow (hydro) Switching to cash crops Agriculture Night irrigation Local Autonomous Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro), Extremes (hydro), Permafrost thaw, Ecosystem Local Autonomous Glacier (hydro) Delay planting until irrigation is available Bolivia Migrating to nearby towns to work Undefined Sharing work between community members McDowell and Hess (2012) Yager (2015) Participatory vulnerability assessment to inform adaptation Bolivia Undefined Migration Bolivia Water Project to support adaptation planning - PPCR Bolivia, Colombia, Ecuador, Peru Agriculture, Project to support adaptation planning - PRAA Biodiversity, Water Colombia Agriculture, Project to support adaptation planning - INAP Habitability, Water Project to support adaptation planning - Macizo Biodiversity, Water Colombiano Temperature, Ecosystem Undefined Formal Policy Agriculture, Hazards, Water Project to support adaptation planning - Proyecto Glaciares; PACC Hazards, Water Project to support adaptation planning - IMACC Ecuador Agriculture, Hazards, Other Climate Change Action Plan Undefined Formal Policy Ecuador Water Construction of infrastructure to transfer water between basins Regional Formal Policy Peru Do Not Cite, Quote or Distribute SM2-62 Huggel et al. (2015) Temperature, Extremes (hydro) Total pages: 87 Temperature, Precip (amount, timing), Extremes (hydro) Temperature, Precip (amount, timing), Glacier (hydro) Anguelovski et al. (2014) Buytaert and De Bièvre (2012) FINAL DRAFT Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Description of Adaptation Scale of Type of relevance / adaptation implementation Peru, Chile Water Establishment of adaptation plan Regional Formal Policy Colombia, Peru Undefined Assessment of adaptation knowledge and needs Global Formal Policy Peru Undefined Migration Local Autonomous Glacier (hydro) Alata et al. (2018) Peru Water National Water Authority Local Formal Policy Temperature, Glacier (hydro) Bury et al. (2013) Undefined GLOF assessment Habitability, Water GLOF prevention program through monitoring and engineering projects Region Country Sector Peru Initiation of GLOFF assessment program Water Water Regional Formal Policy Installation of floodgates to control water level Peru Agriculture, Biodiversity, Culture, Tourism, Water Peru Agriculture Peru Water, Hazards Peru Undefined Undefined Peru Project to support adaptation planning - CGIAR Crop diversification Protection of upstream forests Water Surface storage dams Agriculture Do Not Cite, Quote or Distribute Low-cost gravity drip irrigation system Changing the frequency of irrigation SM2-63 Mills-Novoa et al. (2017) Muccione et al. (2016) Carey et al. (2012) Glacier (hydro), Extremes (hydro) Regional Formal Policy Glacier (hydro) Condom et al. (2012) Local Formal Policy Temperature, Precip. (amount, timing), Glacier (hydro) Doughty (2016) Local Autonomous Potential for multi-purpose projects to address Regional GLOFs and water availability Project to support adaptation planning - CONAM Regional + IGP Project to support adaptation planning - Adapts project Agriculture, Biodiversity Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro) Glacier (hydro), Snow (hydro), Extremes (hydro) Temperature, Extremes (hydro) National System of Hydrological Resource Management Peru Climatic Driver of Adaptation Reference Undefined Temperature, Precip. (amount, timing), Glacier (hydro) Glacier (hydro), Extremes (hydro) Doughty (2016) Drenkhan et al. (2019) Formal Policy Glacier (hydro) Lagos (2007) Formal Policy Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro) Lasage et al. (2015) Regional Local Total pages: 87 FINAL DRAFT Region Country Sector Chapter 2 Supplementary Material Description of Adaptation IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Crop diversification Water Undefined Water harvesting using roof-water systems Establish an integrated regional database on natural resources, climate, and vulnerability. Align the national and regional institutional and legal frameworks to deal with the expected effects of climate change Integrated management of reforestation, soil conservation, terrace management, monitoring systems, and capacity building National Climate Change Strategy Peru Water Hazards Construction of small structures for water storage Regional and distribution and improved management of irrigated areas Integrating existing early warning systems to enhance emergency management Undefined Temperature, Precip. (amount, timing), Glacier (hydro), Extremes (hydro) Lee et al. (2014) Conserving native crop varieties Agriculture Pest management practices Improved pastures and fodder conservation practices Peru Agriculture Peru Agriculture Reducing planting activities Local Autonomous Local Autonomous Crop diversification Moving to livestock based economy to sell milk rather than planting crops Agriculture Peru Agriculture, Energy Do Not Cite, Quote or Distribute Economic diversification Project to support adaptation planning PROCLIM SM2-64 Lennox and Gowdy (2014) Lennox (2015) Precip. (phase state) Livestock, land, and labour diversification Peru Temperature, Precip. (amount, timing), Glacier (hydro) Temperature, Precip. (amount, timing), Glacier (hydro), Extremes (hydro) Local Autonomous Regional Formal Policy Total pages: 87 Temperature, Precip. (amount, timing), Glacier (hydro), Extremes (hydro), Permafrost thaw Precip. (amount, timing), Extremes (hydro) Lopez-i-Gelats et al. (2015) Orlove (2009a) FINAL DRAFT Region Country Sector Peru Agriculture Peru Undefined Chapter 2 Supplementary Material Description of Adaptation Line irrigation canals with cement and install plastic pipes Glacier change assessment in support of adaptation planning IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Local Autonomous Glacier (hydro), Snow (hydro) Orlove et al. (2019) Undefined Formal Policy Temperature, Precip. (amount, timing), Glacier (hydro) Peduzzi et al. (2010) Autonomous Temperature, Precip. (amount, timing), Glacier (hydro), Snow (non-hydro), Extremes (hydro), Ecosystem Postigo (2014) Changing agricultural calendar Increasing pesticide use Peru Agriculture Crop diversification Cultivating in furrows Local Burning shrubs, grass, manure to generate heat Increasing livestock mobility Water Peru Agriculture Peru Water Peru Peru Water Water Water boards regulating water Pasture rotation Creating irrigation channel Local Autonomous Formal Policy Hillside infiltration systems in grasslands Regional Formal Policy Election of water allocator Local Autonomous Making micro dams Undefined Installing water pipes Regional Migration to towns for work Local Local Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro), Ecosystem Temperature, Precip. (amount, timing), Glacier (hydro) Postigo et al. (2008) Somers et al. (2018) Glacier (hydro), Extremes (hydro) Stensrud (2016) Autonomous Glacier (hydro), Extremes (hydro) Wrathall et al. (2014) Autonomous Precip. (amount, timing), Glacier Young and Lipton (hydro), Extremes (hydro) (2006) Formal Policy Livelihood diversification Agriculture Peru Getting grazing rights to other areas Agricultural and crop diversification Water Timed allocation of water-flow to individuals Undefined Seeking foreign funding, skills, attention for help Other Migration Do Not Cite, Quote or Distribute SM2-65 Total pages: 87 FINAL DRAFT Region Country Chapter 2 Supplementary Material Sector Description of Adaptation Biodiversity Conservation corridor IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Formal Policy New Zealand New Zealand Constructing cantilevered bridge to the glacier Tourism Using boats to ferry tourists after glacial lake appeared Regional Autonomous Temperature, Precip. (amount, timing), Glacier (non-hydro) Espiner and Becken (2014) Regional Autonomous Snow (non-hydro) Hopkins and Maclean (2014) Regional Formal Policy Glacier (non-hydro), Snow (nonStewart et al. (2016) hydro) Regional Autonomous Temperature, Precip. (amount, timing), Snow (non-hydro) Demiroglu et al. (2018) Artificial snow production New Zealand Tourism Transitioning to year-round tourism Forming conglomerate business ventures Developing new ski slopes New Zealand Tourism Assessment of stakeholder perceptions for adaptation planning Scandinavia Changing activities at ski area Changing time of use of ski area Norway Tourism Changing ski areas within Norway Artificial snow production Salting glacier surface Norway Tourism Diversifying locations of tourism activity Undefined Autonomous Glacier (non-hydro) Furunes and Mykletun (2012) Norway Energy Water resource and energy directorate Undefined Formal Policy Glacier (hydro) Orlove (2009a) Regional Formal Policy Precip. (amount, timing), Snow (hydro) Aldunce et al. (2016) Southern Andes Chile Undefined Participatory project to identify adaptive options Chile Habitability Local relocation of settlements after GLOF event Local in 1977 Formal Policy Extremes (hydro) Anacona et al. (2015) Chile Agriculture, Energy, Water Impact assessment for adaptation planning Undefined Temperature, Precip. (amount, timing, phase state), Glacier Beniston and Stoffel (2014) Do Not Cite, Quote or Distribute SM2-66 Global Total pages: 87 FINAL DRAFT Region Country Sector Chapter 2 Supplementary Material Description of Adaptation IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference (hydro), Extremes (hydro, nonhydro), Permafrost thaw Agriculture Provide financing and subsidies to farmers Declaration of drought zones Water data system improvement Chile Water Regional Formal Policy Water transfer using trucks Dam construction Traditional water distribution strategies Crop diversification Local Temperature, Precip. (amount, timing), Glacier (hydro), Snow (non-hydro), Snow (hydro) Clarvis et al. (2014) Temperature, Glacier (hydro), Snow (hydro) Hill (2013) Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro) Young et al. (2010) Autonomous Water allocation policy Infrastructure to support irrigation security Policies for drought periods Chile Water Policy to improve irrigation efficiency Regional Formal Policy Policy for better water resources management under increasing scarcity Water allocation policy Autonomous Reinforcing doors and roofs Undefined Couples don't marry to receive subsidy to increase Local portable water Autonomous Migration to areas with more vegetation Chile Agriculture Companies using more efficient irrigation Undefined systems Public funds made available to improve irrigation Regional efficiency Companies securing water rights Water Creating water storage ponds Subsidies made available for single mother for water payments Do Not Cite, Quote or Distribute Undefined SM2-67 Local Autonomous Formal Policy Autonomous Formal Policy Total pages: 87 FINAL DRAFT Region Country Sector Chapter 2 Supplementary Material Description of Adaptation Reducing intake of water canals IPCC SR Ocean and Cryosphere Scale of Type of relevance / adaptation implementation Autonomous Climatic Driver of Adaptation Reference Reduce water use and seize water rights Policy to extend water access Hazards Peru, Chile Water Argentina, Chile, Bolivia Argentina Chile Regional Constructing water canals and pool structures Municipal Emergency Committee provides alerts for harsh seasons Adaptation plan for water management Baseline assessment to support adaptation SSHRC Undefined Baseline assessment to support adaptation - IAI Baseline assessment to support adaptation CLACSO-CROP Habitability, Water, Glacier protection law Argentina Other Glacier protection law Chile Formal Policy Regional Formal Policy Temperature, Precip. (amount, timing), Glacier (hydro), Snow (hydro) Regional Formal Policy Temperature, Glacier (hydro), Montana et al. (2016) Snow (hydro), Extremes (hydro) Regional Formal Policy Glacier (non-hydro, hydro) Anacona et al. (2018) Snow (hydro) Temperature, Precip. (amount, timing), Extremes (hydro), Ecosystem Temperature, Precip. (amount, timing), Extremes (hydro) Da Silva et al. (2019) Mills-Novoa et al. (2017) Western Canada and USA Canada Tourism Artificial snow production Local Undefined Canada Hazards, Habitability Creation of adaptation strategy Local Formal Policy Canada Hazards, Habitability Local Formal Policy Undefined Undefined Glacier (non-hydro), Snow (nonOrlove (2009a) hydro) Global Formal Policy Temperature, Precip. (amount, timing), Snow (hydro) Halofsky et al. (2018) Snow (hydro) Hagenstad et al. (2018) Canada USA Tourism USA Undefined USA Tourism USA Undefined Do Not Cite, Quote or Distribute Creation of steering committee for adaptation planning Artificial snow production Creation of the Sustainable Slopes program Establishment of adaptation partnerships Artificial snow production Diversification of tourism to other seasons/nonsnow reliant Infrastructure to support fish and ranchers SM2-68 Picketts (2013) Picketts et al. (2016) Undefined Local Regional Autonomous Formal Policy Total pages: 87 McNeeley (2017) FINAL DRAFT Region Country Sector Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere Description of Adaptation Scale of Type of relevance / adaptation implementation Climatic Driver of Adaptation Reference Establishment of Tribal Climate Resilience Program Establishment of Climate Science Centers and Landscape Conservation Cooperative Local Temperature, Glacier (hydro), Snow (hydro) USA Undefined Assessment of adaptation knowledge and needs Global Formal Policy USA Tourism Develop alternative tourism (local heritage, wildlife viewing) Local Autonomous USA Habitability Vulnerability analysis and adaptations strategy Local Formal Policy Tourism, Hazards Participatory planning to shift to safer glacier hiking routes Local Autonomous Glacier (hydro), Snow (hydro), Muccione et al. (2016) Extremes (hydro) Glacier (non-hydro), Snow (nonOrlove et al. (2019) hydro) Temperature, Precip. (amount, timing), Snow (hydro), Extremes Strauch et al. (2015) (hydro) Iceland Iceland Do Not Cite, Quote or Distribute SM2-69 Total pages: 87 Glacier (non-hydro) Welling et al. (2019) FINAL DRAFT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 Chapter 2 Supplementary Material IPCC SR Ocean and Cryosphere References Addor, N. et al., 2014: Robust changes and sources of uncertainty in the projected hydrological regimes of Swiss catchments. Water Resources Research, 50 (10), 7541-7562, doi:10.1002/2014wr015549. Adler, C. E., D. McEvoy, P. Chhetri and E. Kruk, 2013: The role of tourism in a changing climate for conservation and development. A problem-oriented study in the Kailash Sacred Landscape, Nepal. Policy Sciences, 46 (2), 161-178, doi:10.1007/s11077-012-9168-4. Alata, E., J. Recharte and B. Fuentealba, 2018: El despoblamiento de la puna: efectos del cambio climático y otros factores. In: Foro International de Ciencias Sociales: Diálogos Interdisciplinarios sobre el Cambio Climático, Desastres y Gobernanza, Cusco, Foro International de Ciencias Sociales: Diálogos Interdisciplinarios sobre el Cambio Climático, Desastres y Gobernanza. Albalat, A. et al., 2018: Climatic trends in snow observations in Andorra. In: International Snow Science Workshop Proceedings Innsbruck, Austria, 586-588. Alberton, M. et al., 2017: Outlook on climate change adaptation in the Carpathian mountains. United Nations Environment Programme, GRID-Arendal and Eurac Research, Nairobi, Vienna, Arendal and Bolzano, 54 pp. Aldunce, P. et al., 2016: Unpacking resilience for adaptation: Incorporating practitioners’ experiences through a transdisciplinary approach to the case of drought in Chile. Sustainability, 8 (9), 905, doi:10.3390/su8090905. Aleynikov, A. A., N. A. Volodicheva, A. D. Olenikov and D. A. Petrakov, 2011: Glacier and avalanche hazards in the recreational complex "Chegetskaya Polyana". Elbrus region, Ice and Snow, 2 (114). Allen, S. K., S. C. Cox and I. F. Owens, 2011: Rock avalanches and other landslides in the central Southern Alps of New Zealand: a regional study considering possible climate change impacts. Landslides, 8 (1), 33-48, doi:10.1007/s10346-010-0222-z. Allison, E. A., 2015: The spiritual significance of glaciers in an age of climate change. Wiley Interdisciplinary Reviews: Climate Change, 6 (5), 493-508, doi:10.1002/wcc.354. Amagai, Y., G. Kudo and K. Sato, 2018: Changes in alpine plant communities under climate change: Dynamics of snow-meadow vegetation in northern Japan over the last 40 years. Applied Vegetation Science, 21, 561-571, doi:10.1111/avsc.12387. Anacona, P. I. et al., 2018: Glacier protection laws: Potential conflicts in managing glacial hazards and adapting to climate change. Ambio, doi:10.1007/s13280-018-1043-x. Anacona, P. I., A. Mackintosh and K. Norton, 2015: Reconstruction of a glacial lake outburst flood (GLOF) in the Engaño valley, chilean patagonia: Lessons for GLOF risk management. Science of the Total Environment, 527528, 1-11, doi:10.1016/j.scitotenv.2015.04.096. Anguelovski, I., E. Chu and J. Carmin, 2014: Variations in approaches to urban climate adaptation: Experiences and experimentation from the global South. Global Environmental Change, 27, 156-167, doi:10.1016/j.gloenvcha.2014.05.010. Archer, D. R. and H. J. Fowler, 2004: Spatial and temporal variations in precipitation in the Upper Indus Basin, global teleconnections and hydrological implications. Hydrology and Earth System Sciences, 8 (1), 47-61, doi:10.5194/hess-8-47-2004. Arkian, F., M. Karimkhani and H. Taheri, 2014: Variability and Trends in the Duration and Depth of Snow Cover in Iran in Thirty Years. Journal of Earth Science & Climatic Change, 5 (10), 1, doi:10.4172/2157-7617.1000239. Atmeh, K., A. Andruszkiewicz and K. Zub, 2018: Climate change is affecting mortality of weasels due to camouflage mismatch. Sci Rep, 8 (7648), doi:10.1038/s41598-018-26057-5. Azhoni, A. and M. K. Goyal, 2018: Diagnosing climate change impacts and identifying adaptation strategies by involving key stakeholder organisations and farmers in Sikkim, India: Challenges and opportunities. Science of the Total Environment, 626, 468-477, doi:10.1016/j.scitotenv.2018.01.112 Babaeian, I., R. Modirian, M. Karimian and M. Zarghami, 2015: Simulation of climate change in Iran during 20712100 using PRECIS regional climate modelling system. Desert, 20 (2), 123-134, doi:10.22059/jdesert.2015.56476. Ballesteros-Cánovas, J. A. et al., 2018: Climate warming enhances snow avalanche risk in the Western Himalayas. Proceedings of the National Academy of Sciences of the United States of America, 115 (13), 3410-3415, doi:10.1073/pnas.1716913115. Balocchi, F., R. Pizarro, T. Meixner and F. Urbina, 2017: Annual and monthly runoff analysis in the Elqui River, Chile, a semi-arid snow-glacier fed basin. Tecnología y Ciencias del Agua, 8 (6), 23-35, doi:10.24850/j-tyca-2017-06-02. Banerji, G. and S. Basu, 2010: Adapting to climate change in Himalayan cold deserts. International Journal of Climate Change Strategies and Management, 2 (4), 426-448, doi:10.1108/17568691011089945. Baraer, M. et al., 2012: Glacier recession and water resources in Peru's Cordillera Blanca. Journal of Glaciology, 58 (207), 134-150, doi:10.3189/2012JoG11J186. Bard, A. et al., 2015: Trends in the hydrologic regime of Alpine rivers. Journal Of Hydrology, 529, 1823-1837, doi:10.1016/j.jhydrol.2015.07.052. Barnett, T. P., J. C. Adam and D. P. Lettenmaier, 2005: Potential impacts of a warming climate on water availability in snow-dominated regions. Nature, 438 (7066), 303-309, doi:10.1038/nature04141. Bavay, M., T. Grünewald and M. 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